By Walt Hunter, Elizabeth Hur, Tim Jimenez

PHILADELPHIA (CBS) – Philadelphia Police are questioning a person of interest in the murder of Officer Moses Walker Jr., a 19-year veteran of the police force who was gunned down in a robbery attempt in North Philadelphia early Saturday morning.

READ: Police Search For Suspects In Fatal Shooting Of Veteran Philadelphia Police Officer

U.S. Marshals surrounded the Bartram Village Apartments at 54th and Elmwood streets in Southwest Philadelphia Wednesday afternoon. The man was taken in handcuffs from a third floor unit sometime after 3 p.m. He was due to report to his probation officer this morning and was picked up on a bench warrant.

Authorities believe the man is the shooter in Officer Walker’s death, but at this time are still classifying him as a person of interest.

In a news conference Wednesday afternoon, Police Commissioner Charles Ramsey said the department is making progress.

“We are pleased with the progress, but until we have enough to charge, there is a lot more work that needs to be done,” Ramsey said. “We still have another person of interest we’d like to bring in, to talk to him about this particular case. So, it’s not over yet.”



Listen to the entire news conference below



While we are not releasing the identity of the person of interest and while he is not charged, court records indicate he was arrested in February 2012 for robbery involving serious bodily harm and possession of illegal weapons, but those charges were withdrawn in June. He we also arrested in 2008 on weapons charges and was sentenced to two to four years in prison.

The latest development comes days after the Philadelphia Police Department released surveillance video of the two suspects following the officer. In the video, Officer Walker can be seen looking several times behind him before being gunned down.

READ: New Video Released Of Suspects Wanted In Officer’s Murder

Police said the suspects apparently announced a robbery, before shooting Officer Walker three times; once on the stomach, chest and hand. He was taken to Hahnemann University Hospital where he was pronounced dead.

Police Commissioner Charles Ramsey announced the reward had reached a record high of $118,000 for information leading to the arrest and conviction of the suspects.

“We would hope that people would step up and help us get two violent people off the street. These guys will rob again. They will kill again if they’re not taken off the street,” said Ramsey.

The first suspect, who police believe is the shooter, is described as a black male, bald head, possibly with a beard or goatee. He was wearing a light-colored hooded sweatshirt and dark-colored shorts.

Authorities continue to search for the second suspect who is described as a black male wearing a dark-colored hooded sweatshirt and dark-colored shorts.

Stay with CBSPhilly for the latest on this developing story.