The killer behind the horrific elementary school killing spree would have seen the children he shot dead as ‘little more than trophies’, an expert psychologist has said. A lone gunman – believed to be 20-year-old Adam Lanza - opened fire at around 9.30am this morning at Sandy Hook Elementary School in Newtown, Connecticut.  It is understood at least 29 people have been killed – including 22 children - and is the worst spree shooting in American history. Professor Craig Jackson, head of psychology at Birmingham City University and an expert in spree killings, said the murderer would have seen killing the children as a way of enacting revenge on those he was angry with. Scroll down for video . Shocking news: At least 29 people are believed to be dead - including 22 children - after a gunman opened fire today at an elementary school in Connecticut . An aerial view of Sandy Hook Elementary School in Newtown, Connecticut, where the worst spree killing in American history happened today . Tragedy: A woman leans on a man as she weeps outside a building set up to counsel family members affected by a shooting nearby at Sandy Hook Elementary School . ‘To him the children are just a lump of meat that happen to help him prove his point,’ he explained. ‘If this was a revenge spree then he would see the children as useful trophies because each death would injure those he wanted to hurt. ‘This was the case in the Dunblane school massacre. Thomas Hamilton had no connection to the school but saw the killing of the children as a way to punish the community as a whole.’ It is understood Lanza headed to the elementary school where he killed the head teacher before targeting a class taught by his mother. Expert opinion: Professor Craig Jackson is the head of psychology at Birmingham City University and specialises in spree killings . Professor Jackson said: ‘It is possible that this spree stemmed from a domestic row and after he killed once, he decided to continue shooting. 'As he had already killed one person, he may have seen keeping on going as the only option. ‘But then the main question is, why shoot the children? There must have been a motive for that. He must have felt he had a grievance with the community that he wanted to punish. ‘Many spree killers target children as a way to get even with the local community. ‘I’m sure many survivors will report that he was calm and focused.  These sort of killers aren’t crazed, they know what they are doing and choose who they kill. 'Victim selection is not random, and statements from many spree survivors describe how something about them, their looks, their history with the killer, or even how they pleaded for their life was able to make the killer's attention shift from them. ‘The Columbine High School massacre is an example of this, where the killers let some people go but shot others dead. 'This makes them feel powerful and in control.’ Professor Jackson explained that all spree killers have certain things in common – they are unstable, narcissistic, immature and consistently blame others for their failures. He continued: ‘They often believe they should be doing better in life than they are doing and believe it is others’ fault that they are not. ‘They may believe teachers held them back, or blame their parents, but it is never their fault. ‘This outlook builds throughout their lives and then it comes to a point that something tips them over the edge.’ He said the killing of his mother points to trouble at home but the thing that sent the killer over the edge could also be down to problems at work or university. The Batman killer James Holmes had been kicked out of his university for failing his exams shortly before his shooting rampage at the midnight screening of the Dark Knight Rises in Aurora, Colorado, on July 20. Stunned: People leave the scene outside the Sandy Hook Elementary School following a shooting inside the school in Newtown, Connecticut . Run: Officers evacuate students from Sandy Hook Elementary . On high alert: Heavily armed Connecticut State troopers at the Sandy Hook Elementary School as young children are evacuated from the scene . Murderer: Adam Lanza, a troubled 20-year-old loner with a history of autistic behavior, is the monster behind a horrific shooting at a Connecticut elementary school that left 26 people, including 20 children, dead . Professor Jackson added that spree . killers are often loners who don’t have partners or children – though . there are some exceptions to the rule, such as Derrick Bird who killed . 12 people and injured 11 others before killing himself in Cumbria, . England, in 2010. He . said: ‘Spree killers are normally aged between their 30s and 40s. This . killer is in his early twenties, so it is unlikely that he had a partner . or a child, but not impossible. ‘It is unusual at his young age to carry out a spree killing at an elementary school. When they are this young, they tend to carry out their shootings at their university campus. ‘A prime example is Seung-Hui Cho, a South Korean student, who killed more than 30 people in a spree killing at Virginia Polytechnic Institute and State University in Blacksburg, Virginia, United States, in 2007. 'Our hearts are broken': American President Barack Obama gave an emotional address to the nation after the killings . Small town: Newtown in Connecticut has a small population of around 60,000 . 'There have also been two spree killings at universities in Germany and another two in Finland in the last eight years. ‘So . it is unusual for a man his age to choose an elementary school. It . appears the main connection must be because of his mother.' But he added it wasn’t surprising that the killer was not taken alive. ‘Many spree killers don’t intend to survive and often will stay alive until police arrive who they will force to shoot them. ‘It is then that police, particularly in America, will start checking the killer’s home for booby traps and weapons. The Batman killer left pipe bombs and booby traps in his apartment. On March 13, 1996, Thomas Hamilton walked into Dunblane Primary School in Scotland and shot 16 children and their teacher dead before turning the gun on himself . Killers: Dylan Klebold and Eric Harris killed 13 people in their rampage through Columbine before taking their own lives in 1999 . Gunman: Jacob Tyler Roberts, 22, opened gunfire at an Oregon mall on Tuesday, killing two people . ‘They often evacuate the street in . case of this but it seems unlikely any would have been set in this case . if he lived with his parents. ‘It also seems that an argument may have triggered the killings rather than a well-thought-out attack.’ But Professor Jackson said his main concern is that the killings will spark a copycat attack. He continued: ‘It is often the case with spree killings that get wide-spread media coverage that another will happen a few weeks afterwards. ‘This was the case with the Batman killer and Dunblane. Three weeks after Dunblane, Martin Bryant murdered 35 people and injuring 21 others in the Port Arthur massacre, in Tasmania, Australia, in 1996. He said he had hoped to beat the number of people that Thomas Hamilton had killed.’ Headlines: Virginia Tech shooter Cho Seung-Hui sent media packages out before his rampage . Madness: James Eagan Holmes killed 12 people in a Colorado movie theater during the midnight screening of the new Batman movie .
Gunman Adam Lanza believed to have killed 29 people - including 22 children - at Sandy Hook Elementary School in Newtown, .
Connecticut, today .
Head of psychology at Birmingham City University Professor Craig Jackson describes what may have been going through the killer's mind .
The killer behind the horrific elementary school killing spree would have seen the children he shot dead as ‘little more than trophies’, an expert psychologist has said. A lone gunman – believed to be 20-year-old Adam Lanza - opened fire at around 9.30am this morning at Sandy Hook Elementary School in Newtown, Connecticut.  It is understood at least 29 people have been killed – including 22 children - and is the worst spree shooting in American history. Professor Craig Jackson, head of psychology at Birmingham City University and an expert in spree killings, said the murderer would have seen killing the children as a way of enacting revenge on those he was angry with. Scroll down for video . Shocking news: At least 29 people are believed to be dead - including 22 children - after a gunman opened fire today at an elementary school in Connecticut . An aerial view of Sandy Hook Elementary School in Newtown, Connecticut, where the worst spree killing in American history happened today . Tragedy: A woman leans on a man as she weeps outside a building set up to counsel family members affected by a shooting nearby at Sandy Hook Elementary School . ‘To him the children are just a lump of meat that happen to help him prove his point,’ he explained. ‘If this was a revenge spree then he would see the children as useful trophies because each death would injure those he wanted to hurt. ‘This was the case in the Dunblane school massacre. Thomas Hamilton had no connection to the school but saw the killing of the children as a way to punish the community as a whole.’ It is understood Lanza headed to the elementary school where he killed the head teacher before targeting a class taught by his mother. Expert opinion: Professor Craig Jackson is the head of psychology at Birmingham City University and specialises in spree killings . Professor Jackson said: ‘It is possible that this spree stemmed from a domestic row and after he killed once, he decided to continue shooting. 'As he had already killed one person, he may have seen keeping on going as the only option. ‘But then the main question is, why shoot the children? There must have been a motive for that. He must have felt he had a grievance with the community that he wanted to punish. ‘Many spree killers target children as a way to get even with the local community. ‘I’m sure many survivors will report that he was calm and focused.  These sort of killers aren’t crazed, they know what they are doing and choose who they kill. 'Victim selection is not random, and statements from many spree survivors describe how something about them, their looks, their history with the killer, or even how they pleaded for their life was able to make the killer's attention shift from them. ‘The Columbine High School massacre is an example of this, where the killers let some people go but shot others dead. 'This makes them feel powerful and in control.’ Professor Jackson explained that all spree killers have certain things in common – they are unstable, narcissistic, immature and consistently blame others for their failures. He continued: ‘They often believe they should be doing better in life than they are doing and believe it is others’ fault that they are not. ‘They may believe teachers held them back, or blame their parents, but it is never their fault. ‘This outlook builds throughout their lives and then it comes to a point that something tips them over the edge.’ He said the killing of his mother points to trouble at home but the thing that sent the killer over the edge could also be down to problems at work or university. The Batman killer James Holmes had been kicked out of his university for failing his exams shortly before his shooting rampage at the midnight screening of the Dark Knight Rises in Aurora, Colorado, on July 20. Stunned: People leave the scene outside the Sandy Hook Elementary School following a shooting inside the school in Newtown, Connecticut . Run: Officers evacuate students from Sandy Hook Elementary . On high alert: Heavily armed Connecticut State troopers at the Sandy Hook Elementary School as young children are evacuated from the scene . Murderer: Adam Lanza, a troubled 20-year-old loner with a history of autistic behavior, is the monster behind a horrific shooting at a Connecticut elementary school that left 26 people, including 20 children, dead . Professor Jackson added that spree . killers are often loners who don’t have partners or children – though . there are some exceptions to the rule, such as Derrick Bird who killed . 12 people and injured 11 others before killing himself in Cumbria, . England, in 2010. He . said: ‘Spree killers are normally aged between their 30s and 40s. This . killer is in his early twenties, so it is unlikely that he had a partner . or a child, but not impossible. ‘It is unusual at his young age to carry out a spree killing at an elementary school. When they are this young, they tend to carry out their shootings at their university campus. ‘A prime example is Seung-Hui Cho, a South Korean student, who killed more than 30 people in a spree killing at Virginia Polytechnic Institute and State University in Blacksburg, Virginia, United States, in 2007. 'Our hearts are broken': American President Barack Obama gave an emotional address to the nation after the killings . Small town: Newtown in Connecticut has a small population of around 60,000 . 'There have also been two spree killings at universities in Germany and another two in Finland in the last eight years. ‘So . it is unusual for a man his age to choose an elementary school. It . appears the main connection must be because of his mother.' But he added it wasn’t surprising that the killer was not taken alive. ‘Many spree killers don’t intend to survive and often will stay alive until police arrive who they will force to shoot them. ‘It is then that police, particularly in America, will start checking the killer’s home for booby traps and weapons. The Batman killer left pipe bombs and booby traps in his apartment. On March 13, 1996, Thomas Hamilton walked into Dunblane Primary School in Scotland and shot 16 children and their teacher dead before turning the gun on himself . Killers: Dylan Klebold and Eric Harris killed 13 people in their rampage through Columbine before taking their own lives in 1999 . Gunman: Jacob Tyler Roberts, 22, opened gunfire at an Oregon mall on Tuesday, killing two people . ‘They often evacuate the street in . case of this but it seems unlikely any would have been set in this case . if he lived with his parents. ‘It also seems that an argument may have triggered the killings rather than a well-thought-out attack.’ But Professor Jackson said his main concern is that the killings will spark a copycat attack. He continued: ‘It is often the case with spree killings that get wide-spread media coverage that another will happen a few weeks afterwards. ‘This was the case with the Batman killer and Dunblane. Three weeks after Dunblane, Martin Bryant murdered 35 people and injuring 21 others in the Port Arthur massacre, in Tasmania, Australia, in 1996. He said he had hoped to beat the number of people that Thomas Hamilton had killed.’ Headlines: Virginia Tech shooter Cho Seung-Hui sent media packages out before his rampage . Madness: James Eagan Holmes killed 12 people in a Colorado movie theater during the midnight screening of the new Batman movie .
believed to be 20-year-old Adam Lanza - opened Elementary School in Newtown, Connecticut.  It is understood at least 29 people have been killed – Jackson, head of psychology at Birmingham City - including 22 children - after a gunman opened mother. Expert opinion: Professor Craig Jackson the Sandy Hook Elementary School following a