The shooting happened at the parking lot of the Villa Rosa Apartments on South Willow Drive in southwest Houston on Friday night.
Houston police said the victim, Humberto Valasquez, 66, received a call from his son. His son said he was involved in a fight with the security guard.
Valasquez took his gun and left his apartment with two other family members, said police.
Natalie Alvarado, who lives in the apartment above Valasquez, said she heard people yelling downstairs and saw them run outside.
“One person go running, saying, ‘Security, security,’ and another person go,” said Alvarado.
When the the guard and Valasquez saw each other, they exchanged gunfire, said investigators. Alvarado said she heard at least five gunshots.
The guard shot and killed Valasquez. The security guard was also shot. He was taken to the hospital with non-life threatening injuries.
Charges against the security guard are pending an investigation.