Texas Mom's Marriage Was Crumbling for Years Before She Shot Two Daughters in Front of Husband: Sheriff

Fort Bend County Sheriff Troy Nehls tells PEOPLE the marriage between Christy and Jason Sheats – which ended last week in a triple shooting when Christy killed their daughters – had been crumbling for years.

Jason Sheats felt his marriage to Christy Sheats had been spiraling downward since 2012, and on that Friday, his birthday, he drew a hard line, he later told officials:

He told her he would be filing for divorce, Nehls says.

They had been texting that day, while Jason, 45, was out, and when Jason returned home he met her in the backyard and reiterated his desire for a split, he told the sheriff's office, Nehls says.

According to Nehls, Jason told Christy, 42, "This would be the last birthday that you are going to ruin." When she called the family together for a meeting in their living room – Jason, Christy and their two daughters, Madison, 17, and Taylor, 22 – Jason thought they would discuss their impending separation, Nehls says.

Instead, "She immediately pulled the weapon out and pointed it at Mr. Sheats and wanted to blame him: 'You made me do this, you're making me do this,' " Nehls says.

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Subsequently, says Nehls, Christy chased her daughters into the street in front of their Katy home, firing multiple times and leaving them both dead before authorities arrived and fatally shot her. According to Nehls, all of this took place in the span of a few minutes, and all while Jason watched, uninjured.

As for why she didn't shoot Jason, Nehls says, "He felt she wanted him to suffer."

Their deaths came four years after Jason's marriage with Christy began to sour, he told officials. "He [Jason] believes she had a very difficult time dealing with the death of her grandfather in 2012," Nehls says. Two months later, Christy's mother died, he says.

The family's history of calls to service to their house also began in 2012, Nehls says, including three calls regarding Christy's attempted suicides. Authorities have said authorities were called to the house 14 times since 2012, though some of those had to do with the Sheats's alarm system.

Nehls says Christy argued with Taylor the same day as the shooting, but he did not know about what. However, he said that Christy wanted to ground Taylor and prevent her from seeing her fiancé.

Authorities have no evidence Christy exhibited violent behavior before the shooting, Nehls says. And though Jason told authorities Christy had depression and anxiety, Nehls says he has no information on what medications she may have been taking, if any, or how often she took them if so.

Nehls says officials did find several guns in the Sheats's home, he says, including the handgun Christy used.

She got it in 2012, too, Nehls says. It was passed down from her grandfather after he died.