Three years ago Friday, a 36-year-old man who was engaged to be married held a door for a man and that man shot and killed him.
The case is cold, but Hollis Johnson's family and police still believe they can find his killer.
"Come forward and say what you did," Johnson's mother, Pauline Johnson, pleaded on Friday.
Johnson was shot the night of Oct. 27, 2014 after he opened the outside door to his secured condominium building on the 1000 block of Chillum Road in Chillum.
Surveillance video footage shows him holding the door for a man who was walking toward him.
Moments later, that man can be seen running away from the building.
Medics rushed Johnson to a hospital, but he died.
Prince George's County police believe Johnson did not know his killer. His mother agrees.
"I believe that the person who did this, they couldn't have known Hollis, because if they'd known him, they would have liked him," Pauline Johnson said.
Johnson was a college graduate who worked for Freddie Mac.
Anyone with information on the crime is asked to call police. Tips can be made anonymously.
"People talk. People say things. So I'm really making an appeal to those who know what might have taken place on that night, that you would come forth and be freed up of what that guilt is inside," Johnson's mother said.