A gunman who killed seven people in rural Missouri before turning the gun on himself was related to at least four of his victims, police said Friday.
Seven people were found dead in four different homes in the sleepy Bible Belt village of Tyrone, in the south-central Ozarks section of the Midwestern state.
The shooter, Joseph Jesse Aldridge, 36, was later found slumped over inside a pickup truck, apparently from a self-inflicted fatal handgun wound.
His mother Alice Aldridge, 74, was meanwhile found dead in a fifth house in Tyrone "from natural causes," the Missouri State Highway Patrol said.
"A motive for the killing has yet to be determined," said State Highway Patrol spokesman Sergeant Jeff Kinder.
Four of the named victims, aged 47 through 52, two male and two female, were all surnamed Aldridge. Investigators believed the shooter was a cousin of theirs.
An autopsy on Aldridge's mother is scheduled for Saturday.
One person survived the massacre and "she is expected to be okay," said Sheriff James Sigman of Texas County, which includes Tyrone.
"A crime like this in any community is major. It's not something we're used to seeing," Sigman told reporters.
Sigman said the shooter, who was armed only with a handgun, had "a minor criminal history," with no serious offences to his name.
Texas County coroner Tom Whittaker suspected Aldridge may have become angry upon discovering that his ailing mother had passed away, the St Louis Post-Dispatch reported.
"We're speculating that he came home and found her deceased and then, for whatever reason, went on a rampage and started killing people," he told the newspaper.
"Right now, with the shooter dead, we don't know... We're in the information-gathering stage." Tyrone is home to about 50 people, Sigman said, in a 97 per cent white county near the Arkansas border in which one in five inhabitants live under the poverty line.
Snowy murder scene
Yellow police tape on Friday surrounded one of the crime scenes, a simple one-story white house with a small front porch, sitting amid a blanket of snow under a blue sky.
First word about the shootings came at 10:30 pm Thursday (0430 GMT Friday) when a juvenile female called the Texas County Sheriff's Office.
She reported hearing gunshots in one of the houses, and fled to a neighbour's home to notify the authorities, Kinder said.
"Responding deputies found two deceased persons" at that first house, he added, then five other victims in three other residences.
"Another (fifth) residence revealed the body of a deceased elderly female who appeared to have died from natural causes," he added, referring to a victim believed to be the shooter's mother.
Police visited other Tyrone homes in the early hours of Friday, telling residents to stay inside and not to open their doors to strangers, the Herald newspaper in the county seat of Houston, Missouri reported.
"This is a horrific tragedy and our hearts go out to the victims of these senseless acts and their families," Missouri Governor Jay Nixon said in a statement.