Dakota Theriot VA Mug

Dakota Theriot, 21, was apprehended in Richmond County, Virginia, after allegedly killing and shooting five people dead Saturday in the Baton Rouge area.

Alleged mass murderer Dakota Theriot has admitted to killing five people near Walker and Gonzales during the weekend and has admitted shooting them with a gun stolen from his father, who was among the dead, the sheriffs of Ascension and Livingston parishes said Tuesday.

“It’s becoming very clear how it happened," Ascension Parish Sheriff Bobby Webre said at a news conference. "Why it happened (is) still very unclear.”

Law officers arrested Theriot and recovered the weapon Sunday after the 21-year-old's day-and-night drive from south Louisiana to the coastal plains of eastern Virginia, where he lived in his early teens. He's being held at the Richmond County jail pending an extradition hearing Friday. If Theriot doesn't fight his transfer, he could be back in Louisiana by the weekend.

Theriot is accused of killing his girlfriend, Summer Ernest, 20; her father, Billy Ernest, 43; and her brother Tanner Ernest, 17; on Saturday at their mobile home north of Walker in Livingston Parish, and then driving to Gonzales in Ascension Parish to kill his parents, Keith and Elizabeth Theriot, both 50. He faces five murder counts, but a decision hasn't been made yet on whether prosecutors will seek to execute Theriot.

Louisiana investigators spoke with Theriot in Virginia but didn't learn a motive. The sheriffs at their news conference Tuesday did explain more about how the killings happened.

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Theriot had begun dating Summer Ernest just recently, and he moved in with the family a couple weeks ago, Livingston Parish Sheriff Jason Ard said. 

On the morning of the shooting, Theriot rode along with Billy Ernest as he dropped off his wife at work.

"They went back to their home, and a short time thereafter, he committed three murders," Ard said.

The autopsies for the three victims killed in Livingston — Summer Ernest, Billy Ernest and Tanner Ernest — showed they were each shot once in the head, Ard said. 

Authorities believe the Livingston Parish shooting occurred about 8 a.m. Saturday. But 911 was not called until about 45 minutes later, when a 7-year-old in the house grabbed her 1-year-old brother and ran over to a neighbor's to explain what was going on. 

"I don't know what was going through a 7-year-old's mind, but I know it's a lot. I imagine that's why it took so long," Ard said.

At that point, the shooting outside Gonzales had already occurred.

The Ascension Parish Sheriff's Office reported receiving a 911 call at 8:43 a.m., while the Livingston Parish Sheriff's Office has said their call came in at 8:47 a.m.

It was the neighbors in Livingston who called law enforcement. But in Ascension Parish, the call came from Keith Theriot, who had already been shot, Webre disclosed Tuesday.

"The dad still had enough life in him to call 911," Webre said. Keith Theriot also declared through his dying breaths that his son was the one who shot him, the sheriff said.

Webre said he could not yet provide a cause of death for Theriot's parents, because the autopsies were scheduled for later Tuesday.

But Webre said it did not take long after responding to the shooting in Ascension to connect the dots. 

"We started comparing information (with the Livingston Parish Sheriff's Office). We quickly found out there was a relation between Dakota and his mother and father and the family in Livingston," Webre said.

The law enforcement officials said they still do not know the precise route Theriot took when he fled from Louisiana to Virginia. But Webre thanked law enforcement in Alabama, Mississippi and Virginia, as well as Louisiana State Police, Crime Stoppers and federal partners for helping in the arrest.

Theriot was taken into custody without incident Sunday morning after he pulled into his grandmother's driveway in Warsaw, Virginia, about two hours south of Washington, D.C.

Detectives from the two Louisiana sheriff's offices spent Monday in Virginia interviewing the suspect and collecting physical, electronic and biological evidence. On his return, Webre said, Theriot will be booked first in Ascension Parish and then transferred to Livingston Parish, where he will be held.

Asked about whether authorities planned to seek the death penalty, Webre deferred to the parish's district attorney. 

"This is a monster. If our DA moves forward with a first-degree murder case, we would not be opposed to that," Webre said.

Follow Caroline Grueskin on Twitter, @cgrueskin.