Attorney Larry Hanna said the Los Angeles police officer, who has not been named, is a good cop who has never been disciplined before. He loves Anaheim and the LAPD, he added.
While some protesters have called him a bully picking on a 13-year-old boy, his attorney said the decisions he made that day were because he feared for his safety.
Hanna said his client, who was captured on video during the incident, was holding the boy for police, worried for his own safety because of what happened before the video started rolling.
FULL VIDEO: Off-duty LAPD officer fires gun during confrontation
"This started with a young man with his hands in his pocket, stating what the officer heard was, 'I'm going to shoot you, I'm going to shoot you,'" Hanna said.
The boy is heard on video saying he didn't say "shoot," he said "sue." Hanna would not say if his client identified himself as an officer beforehand.
MORE: Anaheim crowd clogs streets, surrounds cars in police protest
In the video, things escalate as other teens gather. At least two others then assault the off-duty officer and he falls backward over a hedge, still maintaining his grip on the teen, but his attorney said he is injured.
"He was hit so hard in the face, he was bleeding. He's had medical attention for this. He was almost passed out. There were at least 20 people around him," added Hanna.
The attorney said that's when the off-duty officer made the decision to shoot.
"He was trained to react the way he did, and he fired one round into the ground as a warning shot and it did what it was designed to do: it dispersed the crowd," the attorney said.
Hanna said he's disappointed by comments made by Anaheim Mayor Tom Tait, who said at a press conference he was "deeply disturbed" by what he saw in the video.
"Instead of saying let's wait until we have a fair and open and honest investigation, he's saying that he already doesn't like what he sees," explained Hanna.
The video, which went viral, sparked angry protests that left the officer's parents' house vandalized, along with some neighboring property.
MORE: 24 arrested in Anaheim amid protests against off-duty officer confrontation with teen
A statement from a spokesperson for the city of Anaheim said the mayor and law enforcement officials are conducting a "fair and impartial" investigation into the incident.
The statement read: "Our mayor spoke from the heart on what has been a major event for Anaheim. At the same time, he called for avoiding any rush to judgment and underscored the principle that will guide our investigation...that our constitution ensures equal treatment for all. We can assure everyone that our investigation will be fair and impartial."