Flisk and Peters were killed Friday at a garage near 81st and Manistee. Officer Flisk, an evidence technician, was processing a burglary on Peters' property.
The suspect, Timothy Herring Junior, lives across the alley from the crime scene with his grandmother. Herring, a parolee who was paroled in April, is charged with two counts of first-degree murder.
"We believe the motive was trying to hide an earlier burglary... He was already on parole as it was and didn't want to be apprehended for an earlier burglary," said a Chicago Police Department Commander Keith Calloway of Herring. "Our theory is that this offender... upon seeing Officer Flisk and Mr Peters looking up evidence, to cover his trail he killed both of them."
A second suspect, Timothy Willis, 22, of 7548 S. Yates, is charged with obstruction of justice and unlawful use of a weapon in the murders. Both Herring and Willis will appear in court on Tuesday.
Herring is also charged with one-count of attempted murder and aggravated battery with a firearm in connection to a June 18, 2010 incident.
A neighbor told ABC7 News that Herring has been in trouble for much of his life. He spent three years of a six-year sentence in prison for the armed robbery of a nearby liquor store in 2007. A state prisons spokesperson tells ABC 7 armed robbery is not one of the crimes that qualifies for truth-in-sentencing rules which would have required almost the full sentence be served. In mid-September, the prisoner review board sent him home on parole with electronic monitoring.
"For the folks who get out, it's impossible to have a crystal ball and project what they may or may not do but yeah, it is frustrating when folks get out a little bit early," said Supt. Jody Weis.
Herring was wearing an electronic monitoring bracelet on his ankle when he allegedly committed the crimes. Records from that bracelet's tracking device may be used against him.
"My dad was talking to him, and we were telling him what happened and he said 'yeah, you know if I would have seen him, I would have stopped him,'" said John Walker, suspect's neighbor.
Commander Calloway would not give specifics about Herring's arrest, but said, "We did get a lot of help from the community or else we wouldn't be standing here right now."
Police said both victims' guns were still in their holsters, which leads investigators to believe Officer Flisk and Peters did not know Herring was coming.
"It appears that this individual snuck up on them and they never had a chance to defend themselves," said Weis.
As the news came that suspects were charged in the case, bunting was hung at the Chicago Police Headquarters in Officer Flisk's memory. Officer Flisk was remembered as a humble family man with a solid work ethic and a warm sense of humor.
"He wasn't just a good officer, he was passionate about his job. He was really good at what he did and he really enjoyed the work he did," said Lt Bob Dubiel, forensic services.
"Always a sense of humor. Never got excited. Always real calm even when he was overwhelmed with," said Mike Emmett, CPD evidence technician.
"He was one of those guys. He would make you laugh. You always wanted to be by him. Everybody liked him. There was nobody who didn't like him," said John Zalewski, CPD evidence technician.
"I've got a memorial in my house with four other police officers that I'm directly related to or worked with, and I've got to add one more to my memorial shrine," said John Murphy, CPD.
Officer Flisk had spent the last four years of his 19 on the force working as an evidence technician processing crime scenes.
Visitation for Officer Flisk will be held Tuesday and his funeral will be Wednesday.
Earlier last week, Police Officer David Blake was shot to death inside his SUV, which was parked in a Southwest Side alley, Monday. No arrests have been made in that case.
A visitation was held Sunday for Officer Blake. His funeral will be private.