That image was released during a news conference on Tuesday morning.
The suspects were described as:
Suspect #1: Black male, bald head possibly with a beard or goatee, wearing a light colored hooded sweatshirt and dark colored shorts.
Suspect #2: Black male, wearing a dark colored hooded sweatshirt and dark colored shorts.
The reward fund for information leading to Officer Walker's killer now stands at $118,000.
"These guys will rob again, these guys will kill again if they are not taken off the streets," said Police Commissioner Charles Ramsey during the news conference.
If you have any information about the suspect or the crime you can submit a tip by dialing 215-686-TIPS (8677), text TIP to PPD TIP (773847) or through phillypolice.com.
A previous piece of video was released in a news conference on Monday morning.
Officer Moses Walker Jr., 40, was slain during a stickup by two men as he walked from his north Philadelphia police precinct to a bus stop at around 6 a.m. Saturday. He had just finished his shift and wasn't in uniform, clad instead in shorts and a baseball cap and a large backpack on his shoulders.
"He looked like a young civilian walking down the street, and we think that's why he was targeted," said Capt. James Clark, head of the homicide unit.
The four-minute video shows Walker looking over his shoulder several times as he walks along a streetlight-illuminated sidewalk, followed by grainy footage of two men walking behind him, first on the opposite side of the street and then crossing over. Out of the camera's view further down the block, the 19-year police department veteran was shot.
"I realize we don't have a real clear view of the suspects, but someone may know who they are just by clothing, the way they walk, the fact that they may hang around at that time of morning in that area," police Commissioner Charles Ramsey said. "Let us decide if any information you have is relevant. Do not decide that for yourself."
A third man in the video, who police believe had no involvement in the crime, was a witness to the shooting and gave police some details about what happened.
"Two males approached (Walker), one of which had a gun, a robbery was announced and he demanded money," Clark said. "During this time, the officer attempted to pull out his off-duty weapon ... one of the males fired, striking him three times: once in the chest, once in the stomach and once in the hand."
Police say the suspects likely didn't know Walker was a police officer when they approached him.
Police say Ofc. Walker pulled out his off-duty weapon at which time he was shot in the chest, stomach and hand.
Ofc. Walker, who was unmarried and had no children, was pronounced dead at a hospital in a city where on average nearly one person has been slain every day this year.
Earlier Monday, police pulled over a white Chevy in North Philadelphia and took a person into custody. That person was wanted for a similar armed robbery in the area. While police say they have not made a connection to Officer Walker's killing, they wanted to question that person.
Clark said three or four armed holdups fitting a similar pattern have occurred in the area over the last couple of months and added that the killers probably live near the scene of the crime.
"We know people out there know who they are," he said.