A cop was beaten to death by fellow officers during a simulated mob attack during training, his mum has claimed.
Houston Tipping, 32, died three days after an off-duty accident at the Elysian Park Academy in Los Angeles, California, on May 26.
Houston was acting as a bike instructor during the training. The scenario involved a tussle with another officer, the Los Angeles Police Department said after his death.
Police said: "Officer Tipping fell to the floor and suffered a catastrophic spinal cord injury."
Shirley Huffman, Houston's mum, has filed a notice of claim against the city.
She alleges wrongful death and civil rights violations, the Los Angeles Times reported.
She alleges her son was "repeatedly struck in the head severely enough that he bled" and he suffered multiple breaks in his neck, causing his death
Other officers had previously been injured during this specific exercise, which brings the training into the question, according to the claim.
Spokesman Capt. Kelly Muniz told the paper that the department was investigating the incident internally to see if “there are any changes that need to be made."
In a statement, LAPD Chief Michel Moore said: "The Department is fully investigating the accident in an effort to identify if any additional measures can be taken to ensure such a tragedy is avoided in the future...We grieve this tragic loss.
"I am proud of Officer Tipping's training classmates that immediately sprang into action, initiating CPR and other life-saving measures as well as the work of the L.A. Fire Department.
"I'm also grateful for Dr Kenji Inaba and the incredible medical staff at Los Angeles County USC Medical Center for doing everything they could to save him."
Houston had been with the department for five years and worked as a patrol officer in the San Fernando Valley.
His funeral was on June 22.
His father paid tribute to his son and said: "My son Houston was naturally kind.
“He genuinely cared about people. He had the perfect character to be an LAPD officer.”
The family have set up a GoFundMe to help support his girlfriend Britney after his death.