A former soldier shot and killed an active duty member of the US Army and three children at a home in South Carolina before killing himself, officials said (Picture: AP)

A former soldier fatally shot three of his children and an active duty member of the US Army in the presence of his ex-wife.

Charles Slacks Jr allegedly used a key to enter the South Carolina home of his ex-wife Aletha Holliday on Tuesday night.

Slacks found Holliday in the backyard of the home owned by both of them, speaking with a 38-year-old male co-worker, according to Sumter Police Chief Russell Roark III. Slacks shot the man and went inside the home and upstairs, Roark said.

Holliday followed Slacks, but stopped when he pointed the firearm at her. She did not have her cell phone with her and could not call 911.

The three children and two men were found shot and killed on Whitetail Circle in Sumter, South Carolina, around 11.30pm on Tuesday (Credits: AP)

‘She goes back outside of the residence, where the first individual had been shot, in search of his cell phone, wasn’t able to locate that,’ said Roark, according to WIS. ‘Then she hears several gunshots.’

Holliday said that when she went inside the home on the 100 block of Whitetail Circle in the Woodridge subdivision, she saw Slacks at the top of the stairs. He took his own life, she said.

She then went to check her children’s bedrooms and found all of them shot dead, Roark said. Two were their kids together and the third was Slacks’ stepdaughter.

They have been identified as Aayden Holliday-Slacks, 5; Aaron Holliday-Slacks, 6; and Ava Holliday, 11.

There was no apparent threat to the public and police continued to investigate the incident (Picture: AP)

‘Sumter School District is grieving the loss of three students. Two siblings attended Millwood Elementary School, and another sibling attended Alice Drive Middle School,’ stated District Superintendent Dr William Wright. ‘Our sincere condolences are extended to the family.’

Roark asked for prayers for the family and the community.

‘When you have a situation where little children were sleeping in the comfort of their own bed, and in no fault of their own had their life taken, particularly by a father and a stepfather, that’s difficult for us to rationalize,’ he said.

Slacks had retired from the military.

The active duty Army member died later at hospital. His identity was not immediately released.