Hundreds of protesters rallied in Anaheim, California, Wednesday night after video surfaced of an off-duty police officer apparently firing a gun during a scuffle with a 13-year-old after kids walked on his lawn.

Demonstrators gathered outside the home of the Los Angeles Police Department officer after he was filmed dragging the teen and discharging a single round during the after-school confrontation. The crowd then moved to block nearby streets.

Twenty-four protesters — including 10 men, eight women and six juveniles — were arrested and there were reports of windows being broken and other acts of vandalism, Anaheim police spokesman Sgt. Daron Wyatt said in a statement early Thursday.

The video, shared widely online, appears to show the unidentified officer holding onto the 13-year-old boy while being jostled by the teen’s friends. The tussle continues until the cop pulls the pair into a hedge before pulling out his weapon and firing it. The video does not show how the confrontation began or what led to the incident.

The 13-year-old was arrested along with a 15-year-old and the unidentified officer is on administrative leave while Tuesday’s incident is investigated, the LAPD said earlier.

The Anaheim Police Department is also investigating and has set up a telephone hotline to deal with calls from the public over the incident.

“Like many in the community, I’ve seen the video and I’m very concerned about what it shows,” Anaheim mayor Tom Tait said in a statement. “Anaheim is committed to a full and impartial investigation. Our city will move forward without delay.”

Image: Protesters march towards the off-duty officer's home late Wednesday.

Image: Protesters march towards the off-duty officer's home late Wednesday.

There were no injuries from the gunshot but the teenager’s grandmother told NBC News the boy had suffered “a lot of bruises.”

Jennifer Dorscht, 45, said the boy had been standing up for a 13-year-old girl who had originally been in an altercation with the officer, and accused the officer of using profanity against the kids.

“It’s just a terrible situation. It could’ve been handled completely in a different manner. He’s a good kid,” Dorscht said from the Children’s Hospital of Orange County where the boy was being examined. “He does all the right things, he has a good heart. I think that’s why he stuck up for this girl.”

Prior to Wednesday evening’s protests, the Anaheim Police Department said in a statement it was “investigating the criminal culpability of the off-duty police officer, as well as the juveniles involved,” adding: “The videos posted online do not depict the entire event. Our job is to collect all of the facts and evidence to present the clearest and most accurate information to the District Attorney’s Office as they make their decision on the filing of criminal charges.”

LAPD confirmed the internal investigation and said the confrontation “began over ongoing issues with juveniles walking across the officer’s property.”

It said in a statement that the boy “is alleged to have threatened to shoot the off-duty officer, at which time the officer attempted to detain the male” until local Anaheim officers arrived. “This led to a physical confrontation between the off-duty officer and several other juveniles.”

Image: Protesters gathered outside the off-duty LAPD officer's home in Anaheim.

Image: Protesters gathered outside the off-duty LAPD officer's home in Anaheim.

It said the boy was booked at Orange County Juvenile Hall for criminal threats and battery. A 15-year-old friend was arrested for assault and battery and was released to his parents.

“The case will be presented to the Orange County District Attorney’s Office when it is completed. The names of the involved parties are not being released at this time,” the statement said.

Jennifer Rojas, a policy advocate at the ACLU of Southern California, told NBC Los Angeles the organization is “deeply disturbed” by reports and demanded “a full explanation of why, in an altercation between the police officer and youths, the youths were arrested but not the officer who fired his gun.”

She added: “An officer, even off duty, has an obligation to follow the law and protect public safety, rather than threaten it. The LAPD officer’s actions on the video are grossly irresponsible.”