After Dakota Theriot lost a place to stay a couple of weeks ago, a family took him in.

A new friend, Summer Ernest, allowed him to stay in her father’s Louisiana home, not far from Baton Rouge. That’s just how Summer was, her cousin said, loving and caring to someone in need of help.

But violence devastated the Ernest family this weekend, after the young man they barely knew allegedly went on a shooting rampage and killed the people who helped him. Theriot then drove to his parents’ trailer in a neighboring county and killed them, too, authorities said.

The 21-year-old drove away, setting off a daylong manhunt that spanned several states. He was arrested more than 1,000 miles to the northeast, in rural Virginia, on Sunday morning.

“For someone to do that, someone so young, someone connected to his victims, the fact that the family took him in and this is the end result, it’s kind of jarring for all of us,” said Lori Steele, spokeswoman for the Livingston Parish Sheriff’s Office.

Authorities said they do not know why Theriot, who had been arrested for minor drug possession but had no history of violent crimes, resorted to such violence. They said his parents kicked him out of their trailer a couple of weeks ago, but they do not know why or whether he had been estranged from his family.

Investigators also have not said what specific type of weapon Theriot used or how he obtained it.

The rampage began shortly before 9 a.m. Saturday, when authorities in Livingston Parish received a 911 call about three victims who had been shot, Sheriff Jason Ard said. Killed were Summer Ernest, 20; her father, Billy Ernest, 43; and her younger brother, Tanner Ernest, 17.

Ard said there were two children inside the home, ages 7 and 1. They were not harmed.

Theriot then stole Billy Ernest’s 2004 Dodge pickup truck and drove to Ascension Parish, about 30 miles away, and shot his parents, Elizabeth and Keith Theriot, both 50, inside their trailer, authorities said.

Before he died, Keith Theriot told officers that his son had shot him, Ascension Parish Sheriff Bobby Webre told reporters at a news conference Saturday night.