Nicoh Mayhew, who was slain Wednesday in Seat Pleasant, had witnessed a prior shooting. He was reportedly offered protection but declined.
His grieving mother says detectives warned her a year ago that her son was likely in danger because of it.
"I was told they were supposed to contact me to move me and my kids, but nobody ever contacted me," says Cynthia Dinkins-Mayhew, his mother.
Mayhew was killed and his 2-year-old son was wounded after the shooting in the 6800 block of Seat Pleasant Drive Wednesday morning. The toddler was shot in the arm, but will be OK.
Mayhew was shot as he walked to his mother's apartment.
Prosecutors say they can't be sure yet that he was targeted, but they had offered him witness relocation assistance.
"We offer protection," says Angela Alsobrooks, Prince George's County State's Attorney. "We can't require that they take it and he declined protection."
"I just heard gunshots and when they stopped, I heard the baby crying and just opened the door and reached out and grabbed my grandson into the house because I knew Nicoh was dead," says Dinkins-Mayhew.
Two suspects fled in 4-door black BMW with Maryland tags, police say.
Meanwhile, Dinkins-Mayhew knows whoever killed her son is still out there.
"If they're going to get us, they're going to get us. I made my peace with God," she says.
She says it sends a chilling message to anyone who may consider being a witness.
"They better watch their back. Doesn't look like the law is going to help them. They didn't help me son."
If the court finds Mayhew was killed because he was a witness, the killed could get an additional 20 years behind bars.
The shooting comes as crime is down in Prince George's County.
Homicides are down 35 percent from last year, dropping from 93 murders in 2011 to just 60 in 2012.
Burglaries are also down almost 20 percent from last year, and violent crime has dropped by 7.6 percent. Overall, crime is down 7.6 percent, which equates to roughly 2,200 fewer crimes this year compared with last year at the same time.