The patrol said four of the dead - two couples - were cousins of Aldridge's, ranging in age from 47 to 52. The names of three other victims and a person who was wounded but expected to survive were being withheld until relatives could be notified.
All the victims were adults and were gunned down within a few miles of one another.
Authorities said the motive remained unclear. But as the investigation unfolded, they found Aldridge's 74-year-old mother dead, apparently of natural causes, on a couch at the home she shared with her son, officials said.
She had been under a doctor's care and appeared to have been dead at least 24 hours, Texas County Coroner Tom Whittaker told the St. Louis Post-Dispatch.
Whittaker speculated that the son "came home and found her deceased and then for whatever reason went on a rampage and started killing people."
"This is a horrific tragedy, and our hearts go out to the victims of these senseless acts and their families," Gov. Jay Nixon said. He said crisis counseling will be made available to students and others.
The sheriff's office learned of the attack when it got a call about 10:15 p.m. Thursday from a young woman who said she had fled to a neighbor's home after hearing gunshots in her house, Kinder said.
The neighbor, who refused to give his name, told The Associated Press that the teenage girl was barefoot and clad only in a nightgown when she came running across a snow-covered field full of thickets that left her legs cut up.
"She was crying so hard, but I finally got out of her `My mom and dad have been shot,'" the neighbor said.
When officers arrived at the girl's home, they found two people dead. Authorities later found five more people dead and one wounded in three other homes. The wounded person was taken to a hospital in undisclosed condition.
The patrol identified some of the dead Friday as Garold Dee Aldridge, 52; his 47-year-old wife, Julie Ann Aldridge; Harold Wayne Aldridge, 50; and that man's wife, 48-year-old Janell Arlisa Aldridge.
With a population of about 50, Tyrone is in largely rural Texas County, where the scenic rivers and woods draw canoeists, trout fishermen and deer hunters. The area has seen an exodus of shoe and garment factories over the decades, along with a drop in dairy and poultry farms, County Clerk Don Troutman said.
Set along a narrow, two-lane highway in a remote, hilly stretch, Tyrone consists of a pocket of mobile homes and other small houses but little else, with no restaurants or shops. A couple of general stores are long gone, and the one-room schoolhouse has been converted into a community building, Troutman said.
"There's not even a stop sign there," said Troutman, a lifelong Texas County resident who has been clerk for 36 years. He said of the bloodshed: "We've never had anything of this magnitude before. It's a shock."
Whittaker told the Post-Dispatch that the discovery of the bodies over a several-hour span was numbing, considering that the county averages perhaps one homicide a year.
"At first I thought, `I have three victims,' then we keep finding more victims," he said. "It's kind of like, `Oh, gosh, what have we got here?' It's spread over miles."