Police in Missouri believe the discovery of his dead mother may have triggered a man to embark on a killing spree that left seven dead before he took his own life.
Officials in Texas County are trying to unravel what led the guman, who has not been named, to travel to four separate homes and shoot seven people and injure an eighth late on Thursday evening.
On Friday morning, police said they were trying to determine what lay behind the killings and the relationship between the 36-year-old suspected gunman and the victims.
But officials said they believed the man's discovery of his mother, dead of natural causes, may have been the trigger to set him on a night of violence that has devastated the small, rural south Missouri community.
Texas County Coroner Tom Whittaker told the St Louis Post-Dispatch that the man's mother had been found by police, dead of natural causes and lying on a couch at her home. She had been under a doctor's care and appeared to have been dead at least 24 hours, he said.
Mr Whittaker said investigators were still gathering evidence, but he speculated that the son "came home and found her deceased and then for whatever reason went on a rampage and started killing people."
Police said they were trying to work out all the details of the case.
"I'm sure there is some sort of relationship but I'm not sure what it is," Sgt Jeff Kinder of the Missouri HIghway Patrol said at a televised press conference on Friday mornnig.
Mr Kinder said that police were still working at six "active scenes", including the location where the gunman apparently took his own life. Another person suffered gunshot injuries and was taken to hospital.
He said that police had been called to a one house by a person who called the emergency serives. When they got there, officers found two bodies. They found a further five bodies at three other properties.
"A female made the 911 call. She was at one of the residences when it started," he added.
The killings took place in a small, rural community in Texas County, in the south of the state. Sheriff James Sigman first confirmed the killings to the Houston Herald on Friday morning.
The newspaper later said that a highway patrol man had confirmed the death of the alleged shooter.
One local resident told the newspaper that at 3.45am authorities came to the door checking for people who had been killed or injured. People said they were told to stay in the house and not to open the door to a stranger.Reuse content