A mixed martial arts fighter named War Machine began physically abusing his porn star girlfriend just months after meeting her on an adult film shoot — and that escalated until prosecutors say he told her: “This is it. I’ve got to kill you now.”

Prosecutors on Monday began their case against Jonathan Paul Koppenhaver, who legally changed his name during his 19-fight MMA career, with opening statements of his trial on 34 counts, including attempted murder, kidnapping and sexual assault. The charges stem from an early-morning attack on Aug. 8, 2014, when he found Christine Mackinday asleep with her then-boyfriend in her bedroom, the Las Vegas-Review Journal reports.

Roughly an hour earlier, Koppenhaver and Mackinday — known by her stage name, Christy Mack — had exchanged “I love you” text messages, according to Koppenhaver’s defense attorney, Jay Leiderman.

“And then it all breaks loose,” Leiderman told jurors.

Mack’s boyfriend at the time, Corey Thomas, testified that Koppenhaver attacked him first, biting his face and right arm while throwing non-stop punches. Mackinday, meanwhile, jumped out of bed and called 911.

“Jon, stop,” Mackinday was heard screaming on the call played in court. “You’re going to kill him.”

Koppenhaver continued attacking Thomas until Thomas told the professional fighter: “You gotta kill me, or you gotta let me go.”

Thomas said the fight lasted about 12 agonizing minutes before Koppenhaver asked him if he’d “snitch” if he let him go, News3LV.com reports.

“I’m looking up at the ceiling thinking to myself, ‘I’m going to die in Christy’s bathroom,’” Thomas told the jury of six men and six women. “That’s not how I’m going out.”

Thomas told jurors he suffered a broken nose, dislocated shoulder and other injuries in the attack, which occurred roughly two months after he started dating Mackinday. Koppenhaver let him leave the house after threatening to get his Navy SEAL and Hells Angels biker friends to hurt Thomas if he went to police, the Associated Press reports.

Koppenhaver then allegedly attacked Mackinday after Thomas left the home, leaving her with a fractured left eye socket, two missing teeth, a lacerated liver, broken ribs and other injuries.

Chief Deputy District Attorney Jacqueline Bluth told jurors that Koppenhaver had abused Mackinday during previous incidents, at first striking her in the head and face with an open hand, and slamming her head into a dashboard in another incident.

Leiderman described Mackinday and Koppenhaver as “two damaged people” who had frequent discussions about sex and rape during their relationship.

“Ultimately, the two of them were swallowed up by the personas they had created for themselves,” Leiderman said.

Koppenhaver, 35, who has pleaded not guilty, could face up to life in prison if convicted. He was arrested outside Los Angeles a week after the alleged attack in Las Vegas.

Testimony from Thomas is expected to resume early Tuesday.