"We believe he is going to be our shooter," Homicide Capt. James Clark said.
No charges had been filed as of Wednesday night.
Police sources said investigators also had identified the accomplice in the shooting death of Walker, 40, but hadn't yet taken that man into custody.
"Oh, we'll get him," Police Commissioner Charles Ramsey said, adding that police still have "a lot of work to do" but have "a good, solid lead."
Time and again, Jones, who has a history of gun, theft, robbery and assault convictions, violated probation - yet somehow was able to walk free.
As recently as July 25, Common Pleas Judge Susan Schulman gave Jones strict restrictions for violating parole. He was placed on state house arrest and was ordered to complete community service, maintain employment, complete a GED program and submit to weekly drug screens.
On Aug. 10, Jones submitted a urine sample that tested positive for drugs, according to a source. Jones' probation officer instructed him to come in Aug. 15 for his weekly report and, according to a source, asked a supervisor to approve obtaining a warrant for Jones' arrest for violating his probation.
But no bench warrant was issued at that time.
Three days later, shortly before 6 a.m. Saturday, Aug. 18, Walker, a 19-year veteran of the police force, was gunned down just blocks from his precinct after he finished his shift.
On Wednesday, after Jones failed to report to the probation office, Judge Dembe issued a bench warrant for his arrest for violating probation.
A $118,000 reward, one of the highest in the city's history, was posted for information leading to Walker's killers. It was not immediately clear if the reward played a role in leading officers to Jones.
Jones' run-ins with the law extend back to at least October 2007, when he was 18:
* On April 1, 2008, Jones was sentenced to two to four years in prison, then three years' probation, after being found guilty of numerous gun charges for a January 2008 incident.
* While on probation, Jones was arrested on Feb. 13, 2012, and charged with robbery, possession of a prohibited firearm and recklessly endangering another person, among other charges. But on April 19, the prosecutor wasn't ready and the witness failed to appear. The case was withdrawn June 12.
* All along, Jones was violating probation in the 2008 case. On March 26, 2012, a hearing was continued for that violation, and four months later Judge Schulman put him on electronic monitoring.
* Jones also was arrested when he was 18 in October 2007, but the charges, including aggravated assault, gun possession, and recklessly endangering another person, later were withdrawn.
About 3:30 p.m. Wednesday, police and U.S. Marshals arrived at Bartram Village, a sprawling Philadelphia Housing Authority complex, and removed Jones from a third-floor unit in one of the three-story brick buildings on Bartram Drive.
Neighbors who gathered behind crime-scene tape said Jones does not live at Bartram Village.
"People are always running in here trying to hide," said Alfonzo Reid, who looked on as cops took a K-9 unit into the building from which Jones was removed.
- Staff writer Morgan Zalot
contributed to this report.
Contact Barbara Laker at firstname.lastname@example.org or 215-854-5933. Follow her on Twitter @barbaralaker.