PEOPLE Explains: Estranged Husband Kills Wife and 7 of Her Friends in Texas Mass Shooting

Police say the estranged husband of a 27-year-old Plano, Texas, woman stormed the home they once shared and fatally shot her and seven of her friends on Sunday night at a Dallas Cowboys viewing party she hosted.

The gunman, identified as 32-year-old Spencer Hight, was having trouble moving on from the split, victim Meredith Hight’s mother has said.

Here are five things to know about the case, which is the worst mass shooting in Plano’s history.

1. A Friendly Gathering Turns Deadly

On Sunday night at about 8 p.m., a police officer responded to multiple reports of gunshots being fired at a home in a usually quiet neighborhood in Plano, authorities have said.

“She was our only child,” Meredith’s father, Gene Lane, told the Washington Post. “All we know is she is gone.”

Besides Meredith, the deceased victims have been identified as Anthony Michael Cross, 33; Olivia Nicole Deffner, 24; James Richard Dunlop, 29; Darryl William Hawkins, 22; Rion Christopher Morgan, 31; Myah Sade Bass, 28; and 25-year-old Caleb Seth Edwards.

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2. Gunman Killed at the Scene

The officer who responded to Meredith’s Plano home found two shooting victims in the backyard, according to police. Inside the house, he found more victims — and came face to face with Spencer Hight, who was heavily armed with numerous weapons, police said.

Spencer was shot and killed on the spot. “The officer found the suspect inside and ended his shooting spree,” Plano Police Chief Gregory Rushin said at a news conference Monday.

Police are still investigating.

3. Before the Shooting, a Deteriorating Marriage

Meredith and Spencer Hight reportedly got married in May 2011, just after she graduated from the University of Texas at Dallas.

The couple bought a house together about two years ago — the same residence where the shooting took place, Meredith’s mother, Debbie Lane, told the Dallas Morning News.

Two years ago or so, though, the couple’s relationship began to sour, Debbie told local TV station KXAS, with Meredith filing for divorce from Spencer in July. The marriage, Debbie said, was marked by alcoholism and violence.

Leaving made her daughter “the happiest she’d been in years,” she told local station WFAA. “Years.”

4. Suspect ‘Was Not Moving on’

While Spencer had moved out months before, he had only collected the rest of his belongings in the past few days, Debbie told WFAA.

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“I think he saw our comfort, ease and happiness … and her [Meredith] embracing new life, and resented it to the maximum and responded the way he did,” Debbie told the station.

“He was not moving on,” she said. “And she was.”

5. Estranged Husband’s Family Is ‘Sorry’

Spencer’s father, Chester Hight, said his family is devastated by the shooting — grieving the deaths of his son, daughter-in-law and those killed at the party.

“I’m so sorry,” Chester said, according to CBS News. “We knew some of those kids.”

The family, he told the Dallas Morning News, is living a “nightmare.”