The reward has been increased in hopes that someone who can point police to the killer will come forward.
"My brother is gone and he's not coming back," said an emotional Anthony Walker.
The family of Moses Walker, Jr. gathered at the North Philadelphia murder scene to remember a man who was dedicated to his family, his faith and his brother and sisters in blue.
"My son served," said the officer's mother Wayne Walker. "He served everybody. He served the city. He served his family. He served his nieces and nephews. I want to thank God for my son."
"Whatever it was about, it wasn't worth taking his life. You took him away from his family. You took him away from the people who loved him and the people he loved," said Anthony Walker.
Walker was walking home in street clothes after his shift at the 22nd Police District when he was gunned down at Cecil B Moore and 21st early Saturday morning.
Investigators suspect robbery was the motive.
Walker was shot 3 times. His service weapon was found underneath his body, but Commissioner Charles Ramsey says the 19 year veteran of the force was unable to get a shot off.
"Right now, I don't want to give too much information about what we have, but right now we don't have anything that would lead to identification, and that's important."
"This is real, whoever did it; you're going to get caught. You're going to get caught.
Walker was not married and had no children of his own. He's survived by his mother and 6 siblings; a tight knit family struggling over his senseless murder.
"I love my brother, and I know my brother is up there looking down on all of us, and I know he hurt, because we are hurt," said Walker.
Funeral arrangements have not been announced.
There is a $35,000 reward for information leading to an arrest and conviction.