By Mike DeNardo

PHILADELPHIA (CBS) — Mayor Michael Nutter today called on the killers of off-duty Philadelphia police officer Moses Walker to turn themselves in.

Mayor Nutter says that with law enforcement working around the clock to find them, the best thing Officer Walker’s killers could do is turn themselves in.

“Every police officer in this city is looking for them,” Nutter says.  Referring to two recent video surveillance clips made public since the crime (see related story), the mayor added, “Citizens now know what they look like.  We have that image that came out yesterday.  Someone knows who these individuals are.  And we’re going to be on them like white on rice.”

The reward fund for information is up to $118,000.

View Full CBS Philly Coverage of Officer Walker’s Murder

Homicide detectives are sorting through dozens of tips received after the release of the second surveillance video showing two men walking near 19th Street and Cecil B. Moore Blvd. just before Walker was shot to death Saturday morning.

Meanwhile, the Fraternal Order of Police has established a memorial fund at the Police and Fire Federal Credit Union for Officer Walker’s family.  The officer’s funeral is scheduled for Monday.