Updated

An inmate has been charged with second-degree murder in the October beating death of a fellow prisoner at Iowa's maximum-security penitentiary, a prosecutor said Friday.

The death of Michael Whitworth was the first homicide inside an Iowa prison since 2010. It has raised questions about safety at the new Iowa State Penitentiary in Fort Madison.

A criminal complaint dated Thursday alleges that Whitworth and inmate Lha Sam Southideth-Whiten, 35, got into an altercation inside a prison cafeteria on Oct. 20.

Southideth-Whiten punched Whitworth in the face, causing him to fall backward to the floor, according to the complaint signed by Lee County Attorney Ross Braden. He continued to strike his face and head even though Whitworth was bleeding heavily and appeared to be unconscious once he hit the ground, the complaint said, citing surveillance video of the beating.

Whitworth, 46, died of his injuries 10 days later at a hospital. An autopsy ruled his death a homicide caused by blunt force trauma.

Prison records show that Southideth-Whiten ignored a correctional officer's commands to stop during the attack. A prison judge has already held Southideth-Whiten responsible for the death, disciplining him with 180 of detention and stripping him of 180 days of earned time.

To be convicted of second-degree murder, prosecutors would have to show that Southideth-Whiten acted with "malice aforethought" but not premeditation. He faces a mandatory sentence of 50 years in prison if convicted and would have to serve 35 before becoming eligible for parole.

In an interview Friday, Braden said he didn't believe the facts justified a first-degree murder charge, which would carry life in prison.

"It appeared more or less a spontaneous incident between two inmates. I don't believe it was something that was planned out ahead of time," he said. "I don't think they had any prior altercations with each other."

Braden said he "couldn't say for certain" what caused the altercation.

Southideth-Whiten, who is already serving a 45-year term for armed robbery, hasn't had a hearing yet on the murder charge and doesn't have a lawyer.

The Iowa Department of Corrections waited until Election Day on Nov. 8 to announce that Whitworth died due to "an incident," prompting a union that represents officers to accuse the agency of trying to minimize the case.

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Follow Ryan J. Foley on Twitter at https://twitter.com/rjfoley