Accused mass murderer Dakota Theriot was booked on five counts of first-degree murder Monday and ordered held without bail in the Jan. 26 shooting deaths of five people, including his parents, his girlfriend and two members of her family.

Theriot, 21, returned to Louisiana last week from Virginia, where he fled after the killings in Livingston and Ascension parishes. He was booked Monday on two murder counts in Ascension Parish, then transferred to Livingston Parish, where he was booked on three murder counts and an allegation that he stole his girlfriend’s father’s truck for a cross-country escape.

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Theriot is accused of killing Summer Ernest, 20; her father Billy Ernest, 43; and a brother, Tanner, 17; at their home north of Walker and then killing his parents, Keith and Elizabeth Theriot, both age 50, at their home southeast of Gonzales. Each were shot in the head. 

Investigators say Theriot has confessed to the killings and that he used a gun stolen from his father to kill them.

According to the Livingston Parish sheriff and the Ernests’ neighbors and relatives, Summer Ernest had recently started dating Theriot and he moved into her family’s home a few weeks before the killings, after his parents had kicked him out. An aunt said in an interview that, at a gathering a week before the killings, relatives “didn’t get good vibes” when they met Theriot.

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Keith Theriot survived long enough after being shot in the head that he was able to identify his son as his attacker, investigators have said.

After the slayings, Theriot had fled to his grandmother’s house in Virginia, but authorities were present for his arrival there and captured him after he pulled up with a gun in his hand.

Under Louisiana law, authorities can hold Theriot without bail for a first-degree murder charge. One state district judge Monday also set a combined bail of $125,000 on home invasion and illegal use of a weapon counts, and another one set bail at $25,000 for the theft of a motor vehicle count.

Theriot has not yet been formally charged. Under state law, prosecutors must bring any homicide case before a grand jury, and in this case Theriot would face two – one for Ascension Parish and one for Livingston Parish.

Tyler Cavalier, spokesman for 23rd Judicial District Attorney Ricky Babin in Ascension Parish, said prosecutors have not decided whether to seek Theriot's execution.

Given Theriot's history of mental troubles, defense attorneys could also seek a sanity commission, a formalized review by court-appointed mental health professionals, to determine whether he is fit to stand trial.

A funeral is scheduled for Saturday for the three members of the Ernest family.

Follow David J. Mitchell on Twitter, @NewsieDave.