Slain Texas Doctor's Wife Also Murdered Two Years Ago

July 18, 2012 — -- On the second anniversary of their mother's murder, the children of slain Texas doctor Joseph Sonnier were learning the details of their father's murder.

Dr. Joseph Sonnier was found shot and stabbed in his Lubbock, Tex., home on July 11.

Authorities believe that Dr. Thomas Michael Dixon hired a hitman to kill Sonnier because the rival doctor was dating his ex-girlfriend. Dixon, 48, allegedly paid for the murder with three silver bars worth about $9,000.

In a statment to ABC News, Sonnier's sons Joseph A. Sonnier, IV and James Sonnier said: "Sadly, my brother and I also lost our mother two years ago under equally tragic, yet totally unrelated circumstances. Without a doubt, we can say that the two situations have no correlation."

On July 12, 2010, Sonnier's ex-wife Becky Gallegos was shot and killed by her second husband who then turned the gun on himself.

Almost exactly two years later, Sonnier's body was discovered shot and stabbed in his home.

The Sonnier family was gathered for his funeral on Monday when they heard about the arrests of Dixon and accused killer David Shepard.

"Although there were many tears shed, there was also a sense of hope that my father's murder has been solved," the brothers wrote in their statement. "We have supreme confidence in the Lubbock law enforcement system and know that justice will be served.

The brothers had kind words about their late father.

"In addition to being an amazing dad, Joe Sonnier was a highly respected doctor, a mentor to several of the younger pathologists that worked for him at the hospital, a trusted source of wisdom and advice to his brother and sisters, and one heck of a good dancer," they wrote.

The brothers added that their father was very close with his mother, Anna Marie, and that the two spoke twice a week over the phone for hours at a time.

Police went to Sonnier's house after receiving a tearful 911 call from a woman outside his home.

"Somebody has broken a window in the back and the doctor did not show up for work today," the distressed woman said in the call. "I need somebody to hurry."

When the 911 operator asked her what she saw, the woman sobbed, "One of his co-workers went in the his house and she says it's not good."

When authorities arrived at Sonnier's house, they found him shot and stabbed.

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.

A few days later, Shepard's roommate called police and said that Shepard, 51, had tried to commit suicide two days after Sonnier's body was found. The roommate also said that Shepard said 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 a police report.

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

"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.

Dixon and Shepard have both been arrested and are being held on first-degree murder charges, 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. Lubbock attorney Dan Hurley is representing Dixon. Hurley was unavailable for comment when ABCNews.com called him, but he told the Amarillo Globe-News that Dixon "intends to fight this" and that the "allegations are untrue."

Court records do not list a lawyer for Shepard.