Authorities have ruled homicide in the death of a University of Nevada, Las Vegas student who collapsed after taking part in a charity amateur “fight night” organized by his fraternity.

An autopsy determined Nathan Valencia’s death to be a homicide caused by blunt force trauma to the head, but a spokesperson for the agency said that simply means he died at the hands of another, not necessarily as a result of a criminal act.

Valencia’s bereaved family has hired a lawyer to investigate how UNLV’s Kappa Sigma fraternity was allowed to host the off-campus amateur boxing match, which they claim is sanctioned by the university and is held annually.

Valencia’s family said in a statement, “We will leave no stone unturned in determining how a 20-year-old ended up in a school-sanctioned amateur fight that cost him his life.” Valencia, a kinesiology junior, competed in the “Kappa Sigma Fight Night” on Nov. 19 at the Sahara Events Center in Las Vegas.

A cellphone video of Valencia’s boxing match appeared to show him and an opponent wearing protective headgear and boxing gloves as Valencia took several punches to the face and head during the three-round bout in front of what appeared to be a large and boisterous audience.

Valencia collapsed minutes after the fight and was taken to the hospital, where he died four days later, according to his family.

According to Nick Lasso, an attorney for the Valencia family, medical assistance for the student was not immediately available at the event. He also claimed that the fight’s referee was not a professional.

“Our preliminary investigation reveals errors were made and safety precautions were overlooked,” the family said in a statement. “We will be completing a full investigation to determine how UNLV and the Kappa Sigma Fraternity could allow and promote an event like this to take place.”

“College students should not be placed in a situation where they are pitted against each other for combat,” the family added.

According to Lasso, the match between Valencia and his opponent appears to have been billed as the main event despite Valencia’s lack of amateur boxing experience.

“We are shocked and heartbroken as we mourn the loss of one of our own,” said UNLV president Keith E. Whitfield in a statement following Valencia’s death.

“UNLV is devoting all available resources to reviewing the incident and determining how off-campus events like these can be as safe as possible,” Whitfield said in a statement.

The executive director of Kappa Sigma, Mitchell B. Wilson, stated that the fraternity was “greatly saddened by the loss of Nathan Valencia,” but declined to answer further questions about the student’s death. According to a spokesperson for the Las Vegas Metropolitan Police Department, the agency investigated the boxing charity event’s licensing and found “no evidence of criminality on the part of the venue.”

The Nevada State Athletic Commission, which oversees boxing in the state, has announced that an investigation into the Kappa Sigma charity event has begun.

“The NSAC takes this tragedy seriously, and our hearts go out to Mr. Valencia’s family and loved ones,” Nevada State Athletic Commission Chairman Stephen J. Cloobeck said in a statement.

Lacey Foster, Valencia’s girlfriend, said she went to the event and got a “really weird feeling” as soon as she walked in.

“I remember someone’s headgear falling off during one of the fights,” Foster recalled. “You could see during Nathan’s fight that he was just trying to get away to catch a breath.”