His girlfriend's father had warned him to stay away from his house and the dirt track Sweatt had built in the backyard for his all-terrain vehicles.
Then on Tuesday afternoon, Sweatt broke into the parents' house and waited for them and the girlfriend to come home, police said. When they did, Sweatt fatally shot his girlfriend, her parents and two children living there, before turning the gun on himself, Greenwood County Sheriff Tony Davis said.
"Once you see a horrific scene like this it never leaves you. It's with you day in and day out," he said.
The victims were identified as Richard Fields, 51; his wife, Melissa Fields, 49; their daughter Chandra Fields, 26; and two of the couple's grandchildren who lived with them: William Robinson, 9; and Tariq Robinson, 11.
Davis didn't specify a motive for the shootings, but said it appears they stemmed from a "domestic violence situation."
He said Sweatt felt that Chandra Fields wasn't allowing him to see their infant child often enough. The girl was not among the dead.
He said that Sweatt had called 911 while he was in the Fields' house, stating that he was on the edge and contemplating suicide, before hanging up.
It's unclear how many — if any — victims had been shot before he made the call at 5:54 p.m. Tuesday. A police report said a dispatcher heard a woman in the background say: "Do not point that at me" before the call was disconnected.
Sweatt allowed four children to escape — his 7-month-old daughter, the infant's cousin and two neighborhood children who came to the door after school to play with the Fields' grandchildren.
No one knows why Sweatt let them live and shot the others, Davis said.
"I cannot tell you at this point that I have all the answers for you," he said.
While they're still searching for clues, one thing is clear: Sweatt's life was spinning out of control.
Sweatt has a lengthy arrest record that dates back nearly a decade, according to state police records. Most of his charges were related to property crimes, such as burglary or forgery, although he was arrested once on aggravated assault charges.
He was supposed to be in court Tuesday on a burglary charge, Davis said. The sheriff didn't have many details about the hearing, but said Sweatt faced up to 30 years if he was convicted.
On July 6, 2012, a woman filed a complaint, saying she wanted to have Sweatt checked out because he was threatening suicide, according to a Greenwood County sheriff's office report. She also said she was afraid of him. No charges were filed.
Neighbors said that a few months ago Richard Fields started allowing Sweatt to store his recreational vehicles on his property. The Fields lived in a one-story home on a rural stretch of road south of Greenwood, a city of about 23,000 in northwestern South Carolina.
Neighbor Jeff Hicks said he didn't mind initially but things quickly changed. Strangers began showing up and racing the four-wheelers long into the night, he said, adding that Fields had complained to him about the noise and said he was going to ask Sweatt to stop coming around.
"He just couldn't take it anymore. He was just fed up," Hicks said.
Hicks said he had frequently talked with his quiet, friendly neighbor about hog hunting and other outdoor activities.
"It's a shame. It just tears you up," said Hicks, who last saw Fields Tuesday morning. "I waved to him, and now I'll never see him again. That's how short life is."
On Wednesday morning, Hicks showed an Associated Press reporter the shed and backyard that still houses more than half-a-dozen four-wheelers. Children's toys and a plastic slide were strewn about an adjoining back yard.
Sheriff Davis said Fields also believed that Sweatt had stolen property from him and told him "not to come back."
But on Tuesday, Sweatt returned.
After breaking in, he waited for the victims to come to the house.
Officers went to the home after receiving the 911 call from Sweatt. Davis said while police were on their way, a neighbor called 911 saying four children from that address had arrived at her house and told her a shot had been fired. He said the children remained at her house.
After about an hour and "several unsuccessful attempts" by officers to make contact with anyone in the home, the SWAT team entered and discovered the bodies, authorities said.
"This is a tragedy," said neighbor Ansel Brewer. "It just so hard to imagine something like this going on here. Why would someone do this?"