Their attorney says corrections officers were playing a "gladiator game" when Carlos Perez, 28, was killed.
Family members use such words as "cover up" and "murder" when describing how Perez died. They have sued the state of Nevada.
The family tells News 3 the suit, filed Tuesday, is not about money; it's about getting answers after their loved one was shot and killed by a correction officer.
"We went to the prison, with my sons," Myra Perez said. "That warden shook our hand, got us water, sat us at a table and never told me my son was shot and killed."
The warden at the prison at Indian Springs is Dwight Neven. According to Transparent Nevada, Neven was paid $141,500 last year, including benefits. The warden has been named in the suit.
Carlos Perez was shot and killed by a corrections officer on Nov. 12. Initially, the family was told their son suffered blunt force trauma. It was days later before they found out he had been shot.
Victor Perez, Carlos' brother, said the funeral home told them he had been shot, not state authorities.
"Would it be possible for us to see him?" Victor says he asked. "He said, 'Well, I'd have to do a lot of work on him due to the gunshot wounds.' That's how we found out there was shots."
The family's lawsuit states that Perez was in administrative segregation, meaning he should not have had contact with other inmates.
The family's attorney, Cal Potter, said that according to a witness and documents obtained from the Department of Prison, Perez was let out of his cell at the same time as another inmate.
The two were handcuffed behind their backs, but began kicking each other when they crossed paths.
The complaint alleges that instead of intervening in the fight, officers let the "gladiator" like scenario continue until an order was given to an Officer Ramos to shoot at the inmates.
Perez was killed; the other inmate wounded.
"The officer should be held accountable," his mother said. "They killed him."
"It's murder," Victor Perez said.
The family does not deny Carlos' troubled past. They said he was serving time for battery, but believe the Department of Corrections withheld information on how he died.
He was scheduled to be released four months after the shooting.
"I want to see justice," Myra Cortez said. "Nobody's son or daughter should have to die that way. We just want to know what really happened and why they lied."
A Department of Corrections spokesperson said they cannot comment on the case because of the pending lawsuit. A report on the incident was sent to the attorney general's office.
In a statement, that office told News 3 they are reviewing the case and will make a decision in the future.
The state has 45 days to respond to the lawsuit filed by the Perez family.
The corrections officers involved are on administrative leave.