CANYON COUNTY — A family gathering turned tragic at a home near Nampa late Christmas night, ending with the shooting death of a nationally known professional mixed martial arts fighter.

The Canyon County Sheriff's Office arrested James Robert Malec, 48, on a charge of second-degree murder in the case. Investigators said Malec shot Justin Mark Eilers, his stepson, after a verbal altercation.

Police reports indicated one witness said Eilers challenged Malec to a fight before the shooting took place.

Malec is a former Canyon County jailer. Eilers, of Boise, was a 1996 Nampa High School graduate.

The incident took place during a gathering at the home of Malec and Eilers' mother late Thursday, Canyon County Sheriff Chris Smith said. He said alcohol was involved and deputies said in court documents several containers of alcoholic beverages were found at the scene.

"They ended up having a verbal altercation," Canyon County Sheriff Chris Smith said. "It was just a personal thing — family issues."

Sheriff's deputies responded to a domestic disturbance in the 4600 block of South Happy Valley Road near Nampa at 10:44 p.m. The call was upgraded to a response to shots fired. Eilers died at the scene of one gunshot wound to the chest, the Canyon County coroner said. A handgun was used in the shooting, Smith said.

A few other individuals were in the home when the dispute took place, Smith said.

A woman who identified herself to police as Eilers' former girlfriend called 911 after the shooting, according to police reports. An argument at the residence began when Eilers and his ex-girlfriend got into a dispute, court documents indicate.

Deputies said in court filings that the former girlfriend is also the mother of Eilers' son. A detective said the woman said Eilers started yelling at her about parenting, the altercation continued to elevate, and she became scared of him. She told investigators she eventually went outside and recalled hearing shouting inside the home, then "two pops," according to a probable cause affidavit used in Malec's arrest.

Investigators said in the affidavit that the dispute erupted between Eilers and Malec inside the house and escalated rapidly, ultimately leading to the shooting. According to the court filing, witnesses saw Malec pointing the gun at Eilers even after Eilers had been shot.

During an interview with police, investigators said in the affidavit, Malec said: "I don't know, this happened, they thought I was going to kill everybody."

Police reported finding a .45-caliber pistol on a kitchen counter inside the home along with a clip holding ammunition. A Canyon County detective indicated that Malec's wife told police her husband carries a weapon "all the time."

When deputies arrived on the scene of the incident, Eilers was lying in the home and Malec was taken into custody. Emergency response workers could not revive the victim, who had been shot in the chest.

Eilers was 19-7-1 as a professional MMA fighter, had fought for the Ultimate Fighting Championship and appeared in matches on CBS and Showtime. He also coached fighters in Boise.

"He trained hard, he trained all the time," said Brandon Shuey of Boise, Eilers' roommate. "He was a real outdoors type of guy. That's about it. He trained and he fished and he hunted."

Malec worked as a Canyon County jailer and dog handler for about two years about eight to 10 years ago, Smith said.

Eilers played football for Iowa State University. He also had wrestled in high school, according to a mixed martial arts Web site.