The gunman was identified as Richard Dale Crum, 51, and was charged with first-degree murder, Tate County Sheriff Brad Lance told reporters.
Six people were shot dead on Friday in multiple locations in a rural hamlet in Tate County, Mississippi, and a suspect was in custody, according to media reports, citing the county sheriff.
Among the victims are a man fatally shot in a store and a woman killed inside a home, WMC-TV reported, citing Tate County Sheriff Brad Lance.
The shootings all occurred in Arkabutla, a community of fewer than 300 people about 40 miles (64 km) south of Memphis, Tennessee.
A suspect, who was unidentified, was taken into custody without incident after being spotted by authorities inside a vehicle, WMC reported.
Four more people were later found dead by deputies, according to the report.
Two of those victims were found at a home where the suspect was believed to reside, WJTV-12 television reported, citing the sheriff.
A sheriff's deputy spotted a vehicle fitting the suspect's car description and attempted to stop it. When the driver continued, the deputy gave chase, leading to the driveway of another home, where the suspect was arrested, WJTV reported.
At that home, officers found two more victims, one dead in a car and another dead in the roadway, WJTV said.
The Tate County sheriff's office and the Mississippi State Police did not immediately respond to a Reuters request for comment.
One man who witnessed some of the events at the store said he pulled out his pistol and considered firing at the suspect, who was armed with a shotgun, but decided to hold his fire.
Instead, witness Ethan Cash told Reuters, he tended to a man who was shot inside his car outside the store and found he had no pulse and was unresponsive.
Cash, 18, said he then drew his pistol on another man, who turned out to be the victim's brother, who was injured.
"He said, 'Man, they just shot my brother,'" Cash said. "And I'm like, 'Man, I'm so sorry. Let's make sure everyone is OK.'"
Later, Cash said, he spotted the suspect.
"I was going to start shooting at the guy as he was pulling off and I didn't know who exactly it was and I didn't want to hurt anybody, so I kind of let the officers do that. It's their job, anyways," Cash said.
Mississippi Governor Tate Reeves said on social media he was briefed on the incidents. Authorities arrested a man who is believed to have acted alone and a motive is not yet known, Reeves said.
"Please pray for the victims of this tragic violence and their families at this time," Reeves said.