A lone gunman killed six people including his ex-wife and stepfather Friday at multiple locations in a tiny rural community in northern Mississippi, the sheriff said, leaving investigators searching for clues to what motivated the shocking rampage.

Armed with a shotgun and two handguns, 52-year-old Richard Dale Crum opened fire at about 11 a.m. and killed a man in the driver's seat of a pickup truck parked outside a convenience store in Arkabutla, near the Tennessee state line, Tate County Sheriff Brad Lance said.

Deputies were working the crime scene when a second 911 call alerted authorities to another shooting a few miles away. After arriving at a home, they found a woman, whom the sheriff identified as Crum's ex-wife, shot dead and her current husband wounded.

Lance said deputies caught up with Crum outside his own home and arrested him. Behind the residence they found two handymen slain by gunfire — one in the road, another in an SUV. Inside a neighboring home, they discovered the bodies of Crum's stepfather and his stepfather's sister.

“Everybody has crime, and from time to time we have violent crime, but certainly nothing of this magnitude,” Lance said in an interview. He added: “Without being able to say what triggered this, that’s the scary part.”

Crum, 52, was jailed without bond on a single charge of capital murder, and Lance said investigators were working to bring additional charges. It was not immediately known if Crum had an attorney who could speak on his behalf.

That initial murder charge was for the killing of Chris Eugene Boyce, 59, the man who was shot outside the store. Boyce's brother was in the truck with him at the time and fled, according to the sheriff. Lance added that Crum chased the brother through a wooded area before he escaped unharmed.

“I heard the gunshot from inside my house,” Ethan Cash, who lives near the convenience store, told WREG-TV. “I had just woken up and I look back here, and I see dude walking back here with a shotgun.”

Cash said he went to the scene and found one person who had been shot. He said he checked for a pulse but found none.

An elementary school and a high school in nearby Coldwater both went on lockdown while the suspect was being sought, according to the Coldwater Elementary School Facebook page. A short time later, a second post on the page said the lockdown had been lifted and “all students and staff are safe.”

Arkabutla resident April Wade, who grew up in Coldwater, said both are small communities where most people know each other, “but if you don’t, you know somebody who knows somebody.”

Speaking from a local tire store in the afternoon, Wade said she and her husband were aware of the shootings but had not heard the names of the suspect or victims.

“I think it’s crazy,” Wade said. “You do not expect something like that to happen so close to home.”

The shootings are the first mass killing in the U.S. since Jan. 23, which saw the last of six in a three-week period, according to an Associated Press/USA Today database. It defines a mass killing as four or more people dead, not including the perpetrator.

On Friday night, President Joe Biden released a statement, calling gun violence an "epidemic," and saying that Congress must act.

"We are 48 days into the year and our nation has already suffered at least 73 mass shootings. Thoughts and prayers aren’t enough," Biden said. "We need — need — commonsense gun law reforms. That includes requiring background checks on all gun sales, banning assault weapons and high-capacity magazines, fully closing the boyfriend loophole to keep guns out of the hands of domestic abusers, requiring safe storage of guns, and eliminating immunity for gun manufacturers who knowingly put weapons of war on our streets."

The Bureau of Alcohol, Tobacco, Firearms and Explosives said its agents were providing assistance to the sheriff’s department and state investigators.