July 17, 2012  -- A well-known Texas doctor is being held on first-degree murder charges for allegedly masterminding a love triangle murder-for-hire plot that resulted in the shooting death of another doctor.

Dr. Thomas Michael Dixon, 48, allegedly paid for the murder with three silver bars worth about $9,000.

Dixon is a plastic surgeon based in Amarillo, Texas, familiar to many in the area from his billboards, advertisements and media appearances.

He is charged with hiring David Shepard, 51, to kill Dr. Joseph Sonnier of Lubbock because the rival doctor was dating his ex-girlfriend.

"I cannot recall a homicide case this unique in nature where you have a high-profile doctor hiring someone to kill someone else, especially another high-profile doctor," Lubbock police Capt. Jon Caspell told ABCNews.com.

On July 11, Lubbock cops answered a call regarding a deceased person. When they arrived at Sonnier's house, they found him shot and stabbed, according to police. A window to his house was broken.

Later that day, police interviewed Sonnier's girlfriend and she said that her ex-boyfriend, Dixon, "insisted on still seeing her, even though she was dating Dr. Sonnier," according to a police report.

Police established a connection between Dixon and Shepard when a witness said the two had met the day before Sonnier's body was discovered.

Detectives were then notified that Shepard had sold a 100 ounce bar of silver for $2,750 at an Amarillo pawn shop on June 15, but they weren't yet able to put all the pieces together.

Their break came when they received a tip from Shepard's roommate, who had known Shepard for over 30 years. The roommate told detectives that Shepard was in business with Dixon and that Shepard had tried to commit suicide by slitting his wrists on July 13, two days after Sonnier was found dead, according to a police report.

After the suicide attempt, Shepard told the roommate that he had been watching Sonnier for weeks, that he had been in the doctor's backyard and that he texted Dixon while watching Sonnier.

"David Shepard stated that he shot Dr. Sonnier several times after coming in through a window. David Shepard described what was used to muffle the sound of the gunshots," the police report says. "What David Shepard described was consistent with what was found at the crime scene. This information was not given to the public."

Shepard told his roommate that he had killed Sonnier "due to some triangle as there was a girlfriend that Dr. Sonnier and Michael Thomas Dixon had in common," according to the report.

Dixon paid Shepard for the murder with three silver bars, worth about $3,000 a piece, police said. Investigators believe the bar Shepard had sold at the pawn shop in June was an advance payment for the killing.

The roommate also told police that Shepard had tried to commit suicide a second time and that it was Dixon who treated the cuts.

"Michael Thomas Dixon also told David Shepard to calm down," the police report says. "Michael Thomas Dixon suggested that David Shepard leave for a couple of weeks."

Dixon and Shepard have both been arrested and charged with first-degree murder, but Caspell said the charges could eventually be upgraded to capital murder charges.

"We've never come across anything like this," Caspell said. "Regardless of who they are, we're going to have to handle it like any other homicide case."

Both men are being held on $10 million bonds. Neither man has entered a plea yet and court records do not list lawyers for the suspects.

Authorities have not released the girlfriend's name, but say she has been interviewed by police and is fully cooperating with the investigation.

"She's been cooperative. Obviously, she's been somewhat victimized in all of this," Caspell said. "We do not suspect her in any way, shape or form."

Caspell noted incredulously that despite the extreme circumstances, the motive for the murder is disconcertingly simple.

"It simply just boils down to a dispute over a girl," he said.