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.