TYRONE, Mo. » Residents in a remote area of southern Missouri are trying to come to grips with what could cause a man to kill seven people, including four of his own relatives, in a nighttime shooting spree that spanned four homes.

The shooter, identified by authorities as 36-year-old Joseph Jesse Aldridge, used a .45-caliber handgun to kill two people each at three homes, one person at another, and then himself, in a reign of violence that began late Thursday night. All of the victims lived in or near the tiny, unincorporated town of Tyrone in the rolling hills of Missouri’s Ozarks region, about 40 miles from the Arkansas border. All of the victims were adults.

Texas County Sheriff James Sigman said people generally have felt safe in small towns like Tyrone.

"Start locking your doors," the sheriff said. "The world’s changing.

The motive for the shooting was still under investigation Friday. The few people in town willing to talk about it knew little about Aldridge, described as somewhat reclusive in an otherwise tight-knit area. Some said they’d seen him around and talked to him, but not enough to form an opinion.

Bud Goodman, 71, of nearby Houston, grew up in Tyrone. He knew all of the victims but little about Aldridge.

"I just don’t know what he was doing," Goodman said.

Police are still trying to figure that out, too. Around 10:15 p.m. Thursday, a 15-year-old girl, wearing only a nightgown and no shoes in near-zero temperatures and with cuts on her legs from running through thickets and hardened snow, pounded on a neighbor’s door.

"She was crying so hard," the neighbor, who declined to be identified out of concern for his safety, said. "I finally got out of her, ‘My mom and dad have been shot.’"

The girl called 911 from the neighbor’s home. Sigman said that as officers responded to that call, they received word of another shooting.

The victims at both addresses were related to each other, and to Aldridge. Authorities identified them as two couples, Garold Dee Aldridge, 52, and his wife, Julie Ann, 47; and Harold Wayne Aldridge, 50, and his wife, Janell Arlisa, 48. Both men were cousins of Joseph Aldridge, according to Missouri State Highway Patrol Sgt. Jeff Kinder.

At some point over the next few hours, Joseph Aldridge killed two more men and another woman at two different locations, Sigman said, and injured another woman. Names of those victims, and details about the woman’s injuries, were not released.

The case took another strange twist when authorities went to the home that Joseph Aldridge shared with his 74-year-old mother, Alice. She was found dead at the home, but apparently of natural causes, authorities said. An autopsy was planned to determine if her death was related to the shooting spree.

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."

Sigman said many of the residents of Tyrone are Aldridges. Police, worried that other relatives might be targeted, reached out to all of them, along with family members in other towns, while they searched for Joseph Aldridge in the early hours of Friday. Sigman said he was confident there were no more victims.

Authorities also alerted everyone else in town about the gunman. Jerry Logsdon, who lives near two of the shooting scenes, was awakened by state troopers at 3:30 a.m. "I thought they were going to tell me my cattle escaped," he said. "They said, ‘There’s been a shooting.’"

Around 5:30 a.m. Friday, in neighboring Shannon County, some 25 miles from Tyrone, Joseph Aldridge was found dead of an apparent self-inflicted wound inside a GMC pickup. Sigman said the truck was running and in the middle of a two-lane highway.

Around town, Aldridge was described as a recluse, and it was unclear what, if anything, he did for a living.

Vernetta Lucille Swartz, 76, Joseph Aldridge’s aunt, lives in Hesperia, Calif., but said the family is grief-stricken.

"Two of my nephews and wives were shot, and I guess another nephew was the shooter," she said.