A West Texas plastic surgeon paid someone $9,000 -- in the form of three silver bars -- to kill another doctor who was dating his ex-girlfriend, police alleged Monday.

Dr. Thomas Michael Dixon and David Neal Shepard were arrested by police in Amarillo shortly after midnight, authorities announced. They are suspected of being involved in the death of Lubbock doctor Dr. Joseph Sonnier III.

An arrest warrant affidavit suggests a love triangle between Dixon, Shepard and a woman who was not identified by police. The affidavit alleges Dixon offered Shepard the three bars, each with an estimated value of $3,000, to kill Sonnier, who was chief pathologist for Covenant Health System in Lubbock.

Sonnier was found shot and stabbed Wednesday inside his home in Lubbock, about 120 miles south of the Texas Panhandle city of Amarillo.

Sonnier's girlfriend told an Amarillo police detective that Dixon was her ex-boyfriend and that he "insisted on seeing her, even though she was dating Dr. Sonnier," according to the affidavit, posted online by the Lubbock Avalanche-Journal.

Also, a co-worker of Sonnier told the detective that Sonnier had said that his girlfriend's ex-boyfriend "would not leave her alone," the affidavit says.

Meanwhile, Shepard was found to have sold a 100-ounce bar of silver at an Amarillo pawn shop for $2,750, the affidavit says. His roommate told authorities that Shepard had been watching Sonnier for weeks and texting Dixon.

Shepard told his roommate that he broke into Sonnier's home and shot him several times with a gun Dixon had given him, the affidavit said. He knew several details that investigators had kept private, it said.

Shepard tried to commit suicide in the days after the murder by cutting his wrists, the roommate allegedly told authorities. The roommate said Dixon closed the wounds and "suggested that David Shepard leave for a couple of weeks," the affidavit said.

Lubbock Police Capt. Jon Caspell said Monday that he didn't know when Dixon and the woman broke up. Dixon and Sonnier appeared to have known each other aside from the woman, Caspell said.

Dixon is a well-known plastic surgeon in Amarillo. No one answered the phone Monday at his practice, High Plains Plastic and Reconstructive Surgery. No phone number was listed for Shepard.

Both men are being held in Randall County Jail pending extradition to Lubbock, Caspell said.