Two southeast Nebraska prison inmates who died in a riot May 10 died from “blunt force” head injuries. That’s according to the official death certificates obtained this week by the Omaha World-Herald newspaper.

The death certificates indicate the inmates died within minutes of sustaining their injuries. Each was struck with an object, but officials have not said what kind of object was involved. The report said both Donald Peacock and Shon Collins were victims of homicide.

Johnson County Attorney Julie Smith says her office will request a grand jury be impaneled to hear evidence once the Nebraska State Patrol completes its investigation into the riot and the deaths of the two inmates. The state’s corrections director says the formal investigation is nearly complete. Director Scott Frakes hoped to have the final report in hand by the end of the week.

Both Peacock and Collins were serving time for child-sex charges, and many have speculated that was the reason they were killed.

Ms Smith is resigning her post effective Friday to become take a job as the top attorney for the Department of Correctional Services, which operates the prison in Tecumseh, Nebraska.

Inmates took over housing units, started fires, destroyed plumbing and tore down walls during the riot, which started May 10 and continued into the early morning hours of May 11. Peacock and Collins were found in their cells after the situation was brought under control.