Image copyright Richmond County Sheriff's Office Image caption Police arrested Dakota Theriot at his grandmother's home in Virginia

US police have arrested a man suspected of killing five people, including his parents, in two separate but related shootings in the state of Louisiana.

Dakota Theriot, 21, was caught on Sunday, 1,770km (1,100 miles) away at his grandmother's house in Virginia.

Saturday's shootings were in Livingston and Ascension parishes, south of Louisiana state capital Baton Rouge.

Authorities said the other victims are a woman thought to be his girlfriend, and her brother and father.

Police believe Mr Theriot stole his father's grey and silver Dodge Ram pick-up truck, before driving to shoot his parents, Keith and Elizabeth Theriot.

He had a gun with him at the time of his arrest, which authorities say he dropped without confrontation.

He faces charges of first-degree murder, illegal use of a weapon and home invasion.

What happened on Saturday?

Authorities say Dakota Theriot was in a relationship with 20-year-old Summer Ernest, and that Mr Theriot had been staying with her family for several weeks.

At around 09:00 local time (15:00 GMT), police were called to a trailer park in Livingston parish, where they found Summer, her father Billy Ernest, 43, and her brother Tanner Ernest, 17, shot and killed in their mobile home.

A neighbour told local media two children were in the Ernest home at the time of the shooting, and ran to her home distressed but unharmed.

Shortly after, other police officers were called for "domestic incident" in the city of Gonzales, 25 miles (40km) south of Baton Rouge, Ascension Sheriff Bobby Webre said.

When they arrived, they found Elizabeth Theriot, 51, shot dead in her bedroom, while her husband Keith, also 51, was still alive.

He told the officers that their son, who had recently been told to leave their house and not return, was the gunman. He was taken to a hospital but later died of his injuries.

What do we know about Dakota Theriot?

After the shootings in Louisiana, Dakota Theriot began the 16-hour drive towards his grandmother's home in Warsaw, Virginia.

Police there had been in contact with his grandmother who had feared her grandson would show up. Officers were in the home when Mr Theriot drove up in what was believed to be the stolen truck.

He was taken into custody without incident in Richmond County, Virginia, and will be returned to Ascension to face charges.

Richmond County Sheriff Stephan Smith told the Advocate newspaper that the suspect appeared tired.

"There were some statements made but at this time that's part of the investigation," he said.

"My family met him last weekend at a birthday party and didn't get good vibes from him," Crystal DeYoung, Billy Ernest's sister, told the Associated Press news agency.

Kim Mincks, a neighbour of Keith and Elizabeth Theriot, told the Associated Press that the 21-year-old had been recently kicked out of his parents' home over his drug use.

"His dad kicked him out of here. He did have a violent streak."

In a Facebook page that appeared to belong to him, there was a repost made in June saying "wish i could clear my mind jus for one day" (sic) with a sad emoji.

In May, he posted a message which said: "If you have a problem with me, tell me. Not everyone else."