LOS ANGELES (AP) — A Los Angeles police officer who died of neck injuries suffered during training was beaten by fellow officers in an exercise meant to “simulate a mob,” according to a wrongful-death claim filed against the city by his mother.

Houston Tipping, a five-year veteran of the force, was hurt on May 26 at the police academy. He died three days later.

According to a report from Nexstar’s KTLA, Huffman alleged her son was “repeatedly struck in the head severely enough that he bled” and suffered multiple breaks in his neck, which caused his death.

“It is tragic and we’re all saddened by his loss,” Capt. Kelly Muniz, an LAPD spokeswoman told the Los Angeles Times of Tipping.

The department also said it launched its own investigation into the incident to determine whether any changes that need to be made” or lessons need to be learned, the report added.

Tipping’s mother filed her notice of claim against the city Friday, alleging wrongful death and civil rights violations. Such claims are often a precursor to lawsuits. A police spokesperson said the department could not comment on the claim.