"He didn't deserve a death like this," said the victim's wife Raquel Ortiz as she sobbed.
The shooting happened on the 15000 block of Roscoe Boulevard just before 10 p.m. Ronald Jimenez was working at a nearby store when he heard the gunshots, ran outside and found the uniformed security guard on the ground in a hallway. Paramedics later pronounced him dead at the scene. Police said the security guard's weapon was missing.
The victim was identified by family members as 51-year-old Oscar Vasquez. Many officers who responded to shooting say they knew Vasquez well and described him as a good man who worked hard for his family.
"He was just always a quiet person and just calm and really friendly," said Alma Ortiz, the victim's niece.
Family members said Vasquez worked at the strip mall for several years and never had to use his gun.
"He never did anything to anybody. He never harmed anyone," said Frankie Alvaranga, the victim's nephew. "It just kills me to know that ... he was standing right there and somebody snuck up behind him and shot him on the right side of his head. And he ran off with his gun."
Witnesses have told police that they saw the victim arguing with a man in a hooded sweatshirt just moments before he was shot.
Anyone with information about the shooting was asked to call Los Angeles Regional Crime Stoppers at (800) 222-TIPS.
