A South Carolina man killed his estranged girlfriend before turning the gun on her parents, nephews and then himself, police said.

Bryan Eugene Sweatt, 27, is alleged to have killed five family members, ranging in age from 9 to 51 years old, Tuesday night in Greenwood, S.C., according to the Greenwood Sheriff's Office, which characterized the rampage as a "domestic-related incident."

Just before 6 p.m. on Tuesday night, sheriff's deputies received a call from a man who said "he needed a deputy because he was thinking about hurting himself and then disconnected the line," said sheriff's office spokesman John Long.

While SWAT officers were on the way and the man was still on the line, a 911 dispatcher overheard a woman saying "do not point that at me," according to a police report obtained by ABCNews.com

Just after the police received the call from the man, later identified as Sweatt, a neighbor contacted police to tell them that the children of Sweatt's girlfriend Chandra Fields, 26, came to her home and reported Sweatt had "shot our mother and tied our grandparents up," according to police.

The oldest of the four surviving children later told police that they saw Sweatt tie up their grandparents in a back bedroom. Police have not released the names or ages of the children.

Deputies arrived on the scene followed by a SWAT team and found the bodies of six people inside the home.

The victims included Chandra Fields, who was shot execution style in the head. Her parents Richard Fields, 51, was shot in the upper body, and her mother Melissa Fields, 49, sustained three gunshots.

Fields' two nephews, an 11-year-old and a 9-year-old, were both found dead at the scene, each with a single gunshot wound to the end.

"I cannot tell you, at this particular point, that I have all the answers," Sheriff Tony Davis told reporters Wednesday afternoon.

In nearly four decades of police work, Davis said, he "never had anything of this magnitude."