The family asked for the public's help to find Williams' killer during a press conference Tuesday at Los Angeles City Hall.
"I'm never going to be the same," said Williams' wife, Rosemarie. "This is not okay. It's not okay for someone to be gunned down and murdered."
Authorities said there are no suspects, no motive and no apparent gang involvement.
The Los Angeles City Council approved a $50,000 reward for information leading to the arrest and conviction of the killer.
"If this was your father and you witnessed something, you'd want to step forward and help get these murderers off these streets," Councilman Tony Cardenas said.
Williams was a cook at a Wingstop restaurant near the corner of Sepulveda Boulevard and Vanowen Street.
He left work about 1 a.m. and headed east on Vanowen Street toward his mother's house, where his family was gathering to spend Christmas.
One mile from where he worked, a dark-colored, late-model Sport Utility Vehicle was captured on surveillance driving alongside Williams' car.
Just seconds later, investigators said Williams was shot at several times and was hit once in the chest.
He was pronounced dead at a nearby hospital.
"I have another baby, her name is Rayne Williams," Rosemarie Williams said. "She's 16 months old. She has not slept. She's used to sleeping on his chest. That night before he left, I told him I loved him."
"I just want to let people know, if you have any answers, please call," said Williams' 10-year-old son, Amileon. "I miss my dad very much."
Anyone with information on the case is urged to call the Los Angeles Police Department at (800) 222-8477.