A 21-YEAR old man suspected of killing his parents and three other people — including a girl he was dating — was arrested yesterday when he drove up with a gun to his grandmother’s house in Virginia, police have said. 

On Saturday, Dakota Theriot shot and killed three people — the woman believed to be his girlfriend, her brother and father — in Louisiana’s Livingston Parish before taking her father’s pickup truck, driving to neighboring Ascension Parish, and shooting his parents, according to authorities.

Theriot’s grandmother in Warsaw, Virginia, had checked into a hotel on Saturday night, fearing he might show up there, Richmond County Sheriff Stephan B. Smith told reporters.

The woman asked authorities to check her house yesterday morning to ensure it was safe before she returned.

While deputies were there, Smith said, Theriot drove up with a firearm pointed out the window of a pickup. A sheriff’s statement said that deputies sought cover and challenged Theriot, who then dropped the gun and was arrested without incident. Smith said the pickup Theriot drove apparently was the one taken in Louisiana.

In Louisiana, at a trailer where the suspect’s parents lived, drops of blood trailed out to the front steps from the bedroom where Keith and Elizabeth Theriot were shot. In the bedroom, blood-soaked pillows were strewn on a bed, and patches of what appeared to be dried blood were on the floor.

Kim Mincks and Jacob Chastant also lived in the trailer and were friends with the Theriots. Mincks said she was in the house at the opposite end of the trailer when the shooting happened but added that she didn’t hear anything. Law enforcement officers came into her room Saturday morning and woke her.

“They said something terrible happened here. ‘Get up, get dressed and walk outside,’ ” she recalled them saying.

Mincks and Chastant said that Theriot had struggled with drugs over the years, had violent outbursts and had recently been kicked out of the trailer.

“We know he had a drug problem. He got kicked out last Monday because of the drug problem. His dad kicked him out of here. He did have a violent streak,” Mincks said.

Theriot will be brought back to Ascension Parish to be booked on two counts of first-degree murder, home invasion, and illegal use of weapons, a statement by Ascension Parish Sheriff Bobby Webre and Livingston Parish Sheriff Jason Ard said. 

Authorities have identified the victims in Livingston Parish as Billy Ernest (43) Tanner Ernest (17) and Summer Ernest (20).

Summer Ernest and Dakota Theriot were in a relationship and that Theriot had been living with her family for a few weeks, according to police. 

Authorities have said that Keith Theriot survived the shooting long enough to let police know who shot him. According to Webre, officials got a “dying declaration from him, and only enough information to let us know that it was his son that committed this act.”