Dateline: Secrets Uncovered: What happened to Mark Hasse?

Mark Hasse, 57, was a top prosecutor before he was killed in the Kaufman County murder case alongside DA Michael McLelland and his Cynthia McLelland in 2013. The three were murdered as part of a revenge plot orchestrated by a former attorney and justice of the peace named Eric Williams, whose wife aided him in committing the killings.

Hasse was reportedly shot down in the street while walking from his car to the courthouse in broad daylight on January 31, 2013. It was later revealed that the couple targeted him first because Eric, who was prosecuted by two of the victims in a computer monitor theft case, blamed Mark the most for losing his job.

Oxygen's Dateline: Secrets Uncovered revisited the case in a September 2020 episode titled Vendetta. It is scheduled to re-air on Thursday, November 17, 2022, at 9 pm ET. The synopsis reads:

"Beloved by his colleagues, Mark Hasse is a fearless prosecutor; he works to put criminals behind bars and making enemies is a hazard of the job; he doesn't know it, but a killer is lurking and Mark isn't the only target."

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Kaufman County prosecutor Mark Hasse was gunned down in broad daylight by a masked man

On January 31, 2013, Kaufman County's associate district attorney, Mark Hasse, was gunned down by a masked shooter.

The shooter was dressed in all-black and shot the attorney, who was walking on the 100th block of East Grove Street in Kaufman, Texas, towards the courthouse at eight in the morning. After shooting Hasse, the masked individual rushed to a car and drove off.

Lenda Bush, an ex-cop, happened to be passing by the scene of the crime when she was on her way to the courthouse. She saw the shooting as well as the shooter, whose body and face were concealed. She said that the shooter got into the car and immediately took off.

Bush called 911 while pursuing the vehicle for nearly three blocks before the shooter escaped. She then raced back to the crime scene and was seen performing CPR on Hasse on a dashboard cam of a police vehicle.

Authorities quickly started looking for the murderer and finding the getaway car was the first thing to do on their agenda. Eric Williams was the first person they suspected of killing Hasse. However, there was no proof of his involvement in the crime up to that point.

People even turned their attention to the Aryan Brotherhood gang in Texas, but they were quickly eliminated as suspects as well.

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The Michael and Cynthia McLelland double homicide was connected to Mark Hasse's murder case

Two months after Mark Hasse's murder, the community was still living in fear and trying to recover from it when two shocking killings rocked the tight-knit city. These were the murders of Michael McLelland and his wife Cynthia. The couple's bodies were found riddled with bullets inside their house.

After the double homicide was connected to Hasse's killing, authorities began to believe that they may have a serial killer on the loose. Authorities were given several fake leads throughout the course of the investigation.

However, they also received an anonymous tip just one day after the McLelland shootings that helped them put their complete focus on Williams. He was once prosecuted by Mark Hasse and Michael McLelland on a theft charge that cost him his job. They soon uncovered more evidence that confirmed his involvement in the killings.

In April 2013, Eric Williams was charged with capital murder for the shootings of Michael and Cynthia McLelland, and prosecutor Mark Hasse. He was tried for the killing in December the following year and was found guilty of capital murder. Williams was sentenced to death. Additionally, his wife Kim Williams also admitted to her role in the murder as the getaway driver and pleaded guilty, receiving a 40-year term.

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Dateline: Secrets Uncovered airs with Mark Hasse's murder and the McLelland Killings this Thursday.