Three teenagers dressed in black and wearing masks and gloves were killed by a resident when they broke into a home, Oklahoma authorities said Monday.
A fourth suspect, the alleged getaway driver, now faces first-degree murder counts in their deaths, authorities said.
The 23-year-old son of the homeowner fired the fatal shots from a AR-15 semiautomatic rifle, officials said. One suspect had a knife, and another carried brass knuckles.
"Preliminary investigation looks like it's self-defense," said Wagoner County Sheriff's Deputy Nick Mahoney, cautioning the investigation was continuing into the midday home invasion.
The shooter voluntarily spoke with investigators. Neither he nor his father was hurt.
The deceased suspects were 16, 17 and 19 years old, the sheriff's office said.
A 21-year-old woman, who Mahoney said may have been a getaway driver, turned herself into Broken Arrow police shortly after the shooting.
Elizabeth Rodriguez was arrested on three counts of first-degree murder, one count of first-degree burglary and one count of second-degree burglary, Chief Deputy Les Young said. She is in the Wagoner County jail.
Rodriguez went to police in Broken Arrow, a Tulsa suburb, and told them she was involved, he said.
Oklahoma state law says that first-degree murder occurs if "any other person takes the life of a human being during ... first degree burglary." Another condition is if a person causes the death of another person with "malice aforethought."
Shortly before 12:30 p.m. Monday, the suspects broke through a door in the back of the home outside Broken Arrow. The young man, who was there with his father, encountered them.
"There was a short exchange of words, then gunfire happened," Mahoney told reporters.
Two of the suspects were in the kitchen; the other was found on the driveway. The suspects' names were not released. Young said Tuesday afternoon that medical officials are working to confirm their identities.
Mahoney said it did not appear the residents and intruders knew each other.
The homeowner's family is saddened that their son had to take three lives, Mahoney said.
Young told reporters that there is a witness, but he wouldn't say whether the person was in the house or outside. The person "gave some information," Young said.
Authorities said the neighborhood has a low crime rate, but resident Leon Simmons told CNN affiliate KTUL-TV in Tulsa there have been a few burglaries in the past six months.