-LRB- CNN -RRB- -- Milwaukee , Wisconsin , police have arrested a man whose DNA linked him to the bodies of nine women killed over 21 years , officials said at a news conference Monday night . Walter E. Ellis , 49 , was arrested after police matched a DNA swab taken from him last week to the victims . Walter E. Ellis , 49 , was arrested after police matched a DNA swab taken from him last week to DNA left on the bodies of nine women killed since 1986 . Police said eight of the women were prostitutes and one was a runaway involved with drugs . They were all killed within a 3-square-mile area of Milwaukee 's north side . `` This case was solved with shoe leather and science , '' Milwaukee Police Chief Edward A. Flynn said . `` Continuing advances in DNA technology have enabled us to link these homicide cases , and it was good police work pursuing numerous leads that led to the arrest of a suspect . '' The homicides occurred between 1986 and 2007 , police said . See where the bodies were found '' Ellis was charged Monday with two counts of first degree murder relating to two of the deaths : 41-year-old Joyce Mims , who was killed in 1997 , and 28-year-old Ouithreaun Stokes , who was killed in April 2007 . Police said more charges are likely . It was n't immediately clear whether Ellis had obtained an attorney . Police said other victims linked to Ellis through DNA were : Tanya L. Miller , killed in 1986 ; Deborah L. Harris , killed in 1986 ; Sheila Farrior , strangled in 1995 ; Florence McCormick , strangled in 1995 ; Irene Smith , killed in 1992 ; Carron D. Kilpatrick , killed in 1992 , and Jessica Payne , killed in 1995 . Flynn told CNN it was hard for investigators to discern a geographic pattern for the homicides . In the 20-year period , more than 2,000 slayings occurred in Milwaukee , he said -- 200 of them in the same area where the bodies were found . Another challenge investigators faced was the developing technology of DNA evidence . The technology in 2009 far exceeds that available in 1986 or even 2002 , he said . It was only this year that police were able to link the nine homicides with the same DNA pattern . Even then `` we did not have anyone to match our DNA profile against , until we were able to get -LSB- Ellis ' -RSB- toothbrush , '' he told CNN . A Wisconsin law passed in 2000 mandated the DNA collection from convicted felons . Ellis was released from prison in 2001 without having his DNA sample collected , Flynn said . Because his name had surfaced in the investigation and because he was also listed in two FBI databases , authorities decided to investigate him further and were able to obtain the search warrant that allowed them to collect his DNA from his toothbrush , the police chief said . News of Ellis ' arrest shocked those who knew him . `` That was just my ex-boyfriend , '' his former girlfriend , Chanita , told CNN affiliate WISN-TV . She asked that her last name not be used . `` I did n't know nothing about nothing like this . I 'm getting shivery now cause you 're talking about some strangling stuff . Lord have mercy on me . I 'm just a wreck right now . I ca n't believe this . I 'm trembling in here . I 'm shakin ' . '' Chanita said she dated Ellis for four years . `` I ca n't believe it . This is a shock , '' she told WISN . `` I got like goose bumps on my arms instantly when you told me that . I 'm like no way -- not Walter -- I ca n't see him hurting nobody . '' For relatives of the victims , the news brought mixed emotions . `` I knew they was gon na get him , I knew it , '' Patricia Donald , best friend of victim Deborah Harris , told WISN . `` Finally he ca n't hurt nobody anymore . '' For her and others , like Sandy Farrior , whose daughter Sheila was linked to Ellis , it was news that helped bring closure . `` Late justice is better than no justice , '' he told WISN . In addition to advances in DNA technology , officials attributed the break in the case to the repeated investigation of cold cases by the Milwaukee Police Department 's Homicide Task Force Cold Case Unit . Although Mims and Stokes were strangled about a decade apart , similar DNA on their bodies helped lead police to a suspect . Watch where cops got DNA sample '' Mims was found strangled and lying on her back wearing only socks on June 20 , 1997 , in a small closet near a living room in Milwaukee , according to court documents . Police found DNA on her body , but there were no matches in the system , the court documents show . On April 27 , 2007 , Stokes was found strangled , partially clothed and lying face down in a living room in Milwaukee , according to court documents . When lab technicians tested the DNA found on her body , they found it directly matched the DNA found on Mims . On August 29 of this year , armed with a search warrant , police took a toothbrush and razor from Ellis ' home . Testing showed the DNA found on Mims and Stokes was a match to Ellis , according to court documents . Ellis has been charged at least 10 times with varying offenses ranging from violent crimes to property crimes between 1981 and 1998 , though some of the charges were dismissed , online court records in Wisconsin show . He was sentenced to five years in state prison after he pleaded no contest to a reckless injury charge in 1998 . None of the victims linked to Ellis was killed during the time he was in jail . However , two men were charged in slayings later linked to Ellis , according to the Milwaukee Journal Sentinel . Curtis McCoy was charged in October 1994 with killing Kilpatrick , but he was later acquitted by a jury , the newspaper reported . It also said Chaunte Ott , who was convicted of killing Payne , served 13 years in prison before being released in January , after DNA analysis showed semen found on the girl 's body was not his . CNN 's Gabriel Falcon contributed to this report .