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The Texas woman who fatally shot her two daughters on her husband's birthday "wanted him to suffer," a Texas sheriff said Wednesday.

Christy Sheats, 42, called a family meeting in the living room of the family home in Katy last Friday afternoon and then shot 22-year-old Taylor and 17-year-old Madison Sheats, authorities said. Her husband, Jason Sheats, was not injured. Officers shot and killed Christy Sheats when they arrived after she refused to put down her handgun.

In a bombshell news conference Wednesday, Fort Bend County Sheriff Troy Nehls told reporters that Christy Sheats had a history of depression and suicide attempts and was on the brink of divorcing her husband.

The couple's marriage had been in a "downward spiral" since 2012, when Christy Sheats' grandfather, who raised her, died — and the gun she used in the killings had been passed to her from her grandfather, Nehls said.

Related: Texas Mom Who Killed Her Kids Was Separated From Husband, Former Employer Says

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Nehls said Jason Sheats told investigators that he assumed his wife was gathering their daughters to tell them they were divorcing. Instead, she pointed a gun at them, shooting them multiple times — but she didn't fire at him, he said.

Fort Bend County Sheriff's investigators said Christy Sheats (left) shot and killed her daughters, Taylor Sheats (center) and Madison Sheats. via Facebook

"We asked Mr. Sheats for a motive in his own words," Nehls said. "He stated that he felt Christy wanted him to suffer."

Christy Sheats had "ample time and opportunity to shoot and kill Mr. Sheats in the home, but she chose not to," Nehls added. "Mr. Sheats stated that Christy knew how much he loved Taylor and Madison and how much they loved him. By killing his children, Mr. Sheats will have to live the rest of his life with this horrible memory."

Related: Texas Mom Who Killed Her Kids Called 'Family Meeting'

The couple's marriage had been in a "downward spiral" since 2012, when Christy Sheats' grandfather, who raised her, died, Nehls said. But their troubles became explosive in the days before the shooting, when Christy Sheats got into an argument with her oldest daughter, Taylor, who authorities say was due to be married just days after she died.

"Christy wanted to ground her and prevent her from seeing her boyfriend, or fiancé, because she argued with her," Nehls said. "Mr. Sheats did not agree ... and told her it was inappropriate to ground their 22-year-old daughter and prevent her from seeing her fiancé."

That appeared to have been the last straw for Christy Sheats, who had been admitted to a private mental health facility on three separate occasions for attempted suicide, Nehls said. Jason Sheats told investigators that she was suffering from depression, was taking "numerous" medications and was seeing a therapist, he added.

At the time of the shooting, Christy Sheats was unemployed, despite listing herself as the business manager of a Houston tattoo removal clinic on her LinkedIn page. Jason Sheats told police that she drank heavily and that although they had been married for more than 20 years, the couple had been separated several times.

Authorities were looking into a claim by Jason Sheats that his wife had been denied a license-to-carry permit in Texas because of her mental health issues.

Still, "Mr. Sheats obviously did not expect this," Nehls said.

Nehls said Jason Sheats did not want to speak publicly about the shootings but had given the sheriff's department permission to provide details from their in-depth interview Tuesday night.

"He did state she accomplished what she set out to do, and that is to make him suffer," Nehls said.