Story highlights Jonathan Koppenhaver leaves behind a suicide note

His ex-girlfriend says he assaulted her in August

"I'm so cursed," he says after the alleged assault

Mixed martial arts fighter Jonathan Koppenhaver, who is accused of beating up his ex-girlfriend, tried to kill himself in a Las Vegas jail, authorities said.

Koppenhaver, 32, is known as War Machine on the MMA circuit. He allegedly beat adult film actress Christy Mack and a male friend on August 8 -- then went on the run.

Police captured him a week later in his hometown of Simi Valley, California. He's been held at the Clark County Detention Center since then.

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A corrections officer conducting checks at the detention center found him unresponsive in his cell on Tuesday, according to CNN affiliate KSNV.

Suicide note

He was found seated on the floor with a torn piece of linen around his neck, which was attached to his bunk, Officer Jose Hernandez told the affiliate. Koppenhaver, who was unresponsive and struggling to breathe, had left behind a suicide note.

Hernandez cut the linen and called medical personnel, who later cleared the fighter and put him on suicide watch at a medical isolation unit. Details of his suicide note were not released.

The incident occurred on the same day he was supposed to appear in court to discuss a plea deal, according to the affiliate.

'I'm so cursed'

Koppenhaver has said that he'd gone to surprise his ex-girlfriend with a ring when he found her with another man.