NASHVILLE, Tenn. -- A security guard fatally shot a man at a south Nashville shopping complex overnight, police said.

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Metro police said the guard, Jeremy Holmes, 28, was telling people to leave the Marathon Sports Bar at Nipper's Corner, when he got into an argument with Adam Villegas, 34, and Villegas' friend.

Police are investigating the incident as a homicide, but they said Holmes, employed by Security Wise Protective Services, may have been justified in firing his gun.

Holmes said the men began to argue and refused to leave the area. Holmes said he asked Villegas how much he had been drinking and that Villegas replied, "a bunch."

Police said that is when the security guard pulled out his gun.

The passenger then jumped out of the car, but Holmes said Villegas continued arguing with him and started aggressively backing the car out, like he might run over him.

Holmes said he feared for his life and then shot Villegas.

After firing, Villegas tried to drive away but crashed his car into a pole at a nearby shopping center parking lot.

Authorities said Villegas was not armed, but it still could be a justifiable shooting.

"He's a trained armed security guard. He's not going to go out with the intent to harm someone or to injure someone unless there is some type of provocation or unless he's in fear of his life," said Detective Brad Corcoran of the Metro Police Department.

The incident is being investigated as a homicide.

"I mean, anytime you have something like this, it is a homicide, but you've got to say that a homicide is not always synonymous with murder because, obviously, there could be an aspect of justifiable homicide," said Corcoran.

There were several witnesses who also re-enacted what they saw, backing up the security guard's story that the driver was attempting to hit Holmes.

"I'm baffled. It's a tragedy. It’s disgusting; somebody in that occupation that should be able to do something like that and get away with it. I hope not," said bar owner Irene Fagiano.

Holmes has been a licensed guard for three years and has no criminal history.

Police have not charged him but have not ruled out that possibility. All of the evidence will be turned over to a grand jury. An autopsy will also be performed on Villegas.

Holmes has been placed on administrative leave.