Prison guards have been accused of covering up the shooting of an inmate involved in a "gladiator-style" fight.

Officials at one of Nevada's toughest prisons have been slow to release details of the killing, which took place on 12 November.

What is known for certain is two handcuffed inmates - Andrew Arevalo, 24, and Carlos Manuel Perez Jr, 28, brawled in a shower hallway at High Desert State Prison and Perez ended up dead from several shotgun blasts.

Arevalo was declared guilty of murder and put in a punishment area known as "the hole", even though he never touched a gun.

Prison officials acknowledged the killing in November with only a short statement, and for months never mentioned a weapon was involved or that it had been fired by a trainee guard.

They recently withdrew the murder allegation after disclosing the guard's involvement.

Attorneys for both inmates are accusing prison guards of instigating the fight to set up a gladiator-style contest and then trying to cover it up by blaming the surviving prisoner.

"The shooting itself is highly disturbing," said Arevalo's lawyer Alexis Plunkett.

"But it's really over the top that (prison officials) immediately filed a murder charge against Andrew, who was absolutely the victim in every possible way."

The incident started when Arevalo and Perez were both released into a hallway near showers in a segregation unit.

They were soon were on the floor, kicking at each other with their hands cuffed behind their backs.

The trainee guard described in a report how he warned the men to stop fighting, fired one blank, issued more warnings and then fired three live rounds down the hall.

At that point, he said, he stopped to reload.

"They continued kicking each other even though they were bleeding," the guard wrote.

Perez died of gunshot wounds to the head, neck, chest and arms. Arevalo suffered similar wounds but survived.

Lawsuit

Attorney Cal Potter, representing Perez's family in a wrongful-death lawsuit, alleges the trainee guard, another guard and a supervising lieutenant created a "gladiator-like scenario" before the shooting.

He said they released Arevalo and Perez together into the shower hallway, where prisoners are supposed to walk alone.

In January, prison administrators held a hearing and declared Arevalo responsible for murder, assault and battery.

He was sentenced to 18 months in an isolation cell known as "the hole," according to prison disciplinary forms provided to AP news service.

Last week, months after Arevalo was put in isolation, prison officials withdrew the murder and assault allegations after objections from his lawyer and repeated questions from AP.

Prison records provided by Ms Plunkett show Arevalo's term in isolation was reduced from 18 months to 120 days. The battery charge is still pending.

She believes her client was blamed for Perez's death in a botched effort by prison officials to cover up the killing.

She maintains that Arevalo did not kill Perez and only fought to defend himself.

Prison officials "never intended to make this shooting public," Ms Plunkett said. "Andrew never had a gun in his hands. He was handcuffed."

The three unnamed guards are on paid leave.