A former soldier fatally shot three sleeping children inside their South Carolina home before turning the gun on himself Tuesday night, according to police.

Charles Slacks Jr., 42, also shot and killed another soldier, 38, who worked with his ex-wife Aletha Holliday during the disturbing murder-suicide. 

Holliday is a sergeant major in the Army, according to her LinkedIn account.

Slacks and the woman were divorced, but he still had a key to their home in Sumter. He entered the house at almost 10 pm Tuesday night, said Sumter Police Chief Russell Roark at a news conference today.

At first, Slack shot the co-worker in the backyard while the mother attempted to stop him. Slack then pushed past her, went upstairs, and shot the three sleeping children, ages 5, 6, and 11, the police said.

“Little children were sleeping in the comfort of their own bed,” Roark said.

The mother's cell phone was upstairs charging, so she ran to see if her wounded co-worker had a phone she could use. Upon hearing new gunshots, she came back inside and saw her ex-husband at the top of the stairs, where he shot himself, Roark said.

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Roark reported that the murdered co-worker did not have any relationship outside work with Slacks' ex-wife. Investigators are still trying to figure out why Slacks came in the first place and whether he was supposed to have a key. 

“Anybody who has children — anybody who has empathy toward a child dying so violently could understand how that mother is feeling," the police chief said.

42-year-old Slacks killed his own children, 5-year-old Aayden and his 6-year-old brother Aason. He also killed his 11-year-old stepdaughter, Ava.

“It was a long night. This was just an awful thing,” the coroner said.

The Sumter School District grieves the loss of three students.

State Sen. Thomas McElveen, a Democrat who represents Sumter, and is also a young father of three, led the state Senate with a moment of silence.

“As a father, I am absolutely nauseated up here talking about it,” McElveen said.

The identity of the soldier killed has not been released because officials are still trying to determine his next of kin, Baker said.

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