(CNN)Jeffrey Williams admitted he fired the shots that struck two officers in Ferguson, police said, but claimed he wasn't aiming for them. Nonetheless, the 20-year-old from the St. Louis area has been arrested for the shootings of two police officers during last week's protests in Ferguson, Missouri, a prosecutor said Sunday. Williams has been charged with two counts of first-degree assault, a count of firing a weapon from a vehicle and three counts of armed criminal activity, St. Louis County Prosecuting Attorney Bob McCulloch said. He described Williams as a frequent protester in the city -- which some took issue with. Bishop Derrick Robinson, an area organizer, said he spoke to Williams on Sunday. "I asked him why would he say that he was a protester because it makes us look bad -- because so many things that we've done to rebuild our community," Robinson said. "It sets us like five steps back to say that it was a protester who did it, but he admitted to me that he'd never protested." For more than 200 days, protests have taken place in Ferguson since the August shooting death of unarmed black teenager Michael Brown. Ferguson police Officer Darren Wilson was not indicted. At the time of his arrest, Williams was on probation for receiving stolen property. The prosecutor thanked the public for the information that led to the arrest. He said police served a search warrant on Williams' residence where they seized a .40-caliber handgun, "which has been tied to the shell casings that were recovered" at the scene of the shooting. Williams is being held on a cash-only $300,000 bond, McCulloch said, adding that it's possible Williams could face more charges and that others could be charged in the case. One element of the case that authorities have yet to sort out is intent, McCulloch said, adding that Williams has acknowledged firing the shots but has said he wasn't aiming at the police officers. Investigators are not sure they "buy" Williams' claim that he opened fire after a dispute with other individuals, McCulloch said, but he didn't rule it out. "It's possible he was firing at someone else," he said, urging any other witnesses with information to come forward. The shots rang out from a hill overlooking the city's police station shortly after midnight Wednesday, at the end of a protest against the Ferguson Police Department, St. Louis County Police Chief Jon Belmar said at the time. Officers saw "muzzle flashes ... about 125 yards away," Belmar said. "We could have buried two police officers," Belmar told reporters last week. "I feel very confident that whoever did this ... came there for whatever nefarious reason that it was." Public donations poured in to be used toward a reward to find the gunman and any accomplices, Belmar said. Authorities offered a $10,000 reward for information leading to the arrest of person or persons responsible for the gunfire upon the two officers, according to the St. Louis Regional CrimeStoppers website. McCulloch said the tipster whose information led to Williams' arrest is eligible to receive the reward. Protesters said they had nothing to do with the shooting, and that the shots came from a grassy hill away from the crowd. "In no way are they representative of the thousands of people ... who have been protesting," said Antonio French, a St. Louis alderman. Belmar believes someone targeted the police, who have faced heated criticism for months, he said. "These police officers were standing there, and they were shot just because they were police officers," he said. The department has been criticized since the shooting death of Brown and, more recently, since a scathing U.S. Department of Justice report documented a pattern of racial discrimination in the city. Police Chief Thomas Jackson resigned Wednesday. "We are actively addressing the issues that have raised concerns of fairness and fair treatment. We support peaceful protesting. However, we will not allow, nor tolerate, the destructive and violent actions of a few to disrupt our unifying efforts," the mayor of Ferguson and the City Council said in a statement Sunday. While many protesters have decried the Ferguson Police Department, neither of the officers shot last week were from the city. One is from Webster Groves, a St. Louis suburb 13 miles south of Ferguson. The officer -- a 32-year-old with seven years' experience -- was shot at the high point of his cheek, just under his right eye, Belmar said. The other was hit in the shoulder and the bullet came out the middle of his back, Belmar said. He is a 41-year-old officer with the St. Louis County Police Department, who has been in law enforcement for 14 years. Both men have been treated and released. CNN's Carma Hassan, Sara Sidner, Jason Carroll, Shimon Prokupecz, Evan Perez and Alina Machado contributed to this report.
Jeffrey Williams, 20, is charged with two counts of first-degree assault, prosecutor says . Prosecutor thanks the public for leading police to a .40-caliber allegedly used in shooting . Two officers, neither from the Ferguson Police Department, were shot during protests last week .