Prosecutors charged both 17-year-old Cheyenne Blalock and 30-year-old Andrew Hall with first-degree murder Thursday, in the death of Kirstan Patterson, who was also 17 years old.
Mayes County Sheriff Mike Reed said Patterson knew both suspects and went to school with Blalock in Chouteau.
"Be very careful who you hang out with and who you run around, because it can make a difference,” Reed said.
He went on to say, “I promise you your parents would rather get up at 1 in the morning and come and give you a ride home than something detrimental happen to you.”
Mayes County deputies said Patterson's body was found on New Year's Day, just south of Locust Grove at the Spring Creek Boat Ramp on the Neosho River.
Just a few hours earlier deputies took a report for a possible missing or runaway teen. Deputies said they went to the scene and confirmed it was the same girl who was missing. Investigators said she had been shot in the head.
Court documents for 17-year-old Blalock say she told investigators that Hall, her boyfriend, had talked about killing Patterson because of claims of a sexually transmitted disease and wanted "payback."
Blalock told investigators Hall had talked about several ways to kill the teen, and claims on New Year's Eve, he told her to text the victim for him to pick her up.
Blalock said her boyfriend made her ride in the back of his car under a blanket when they picked up Patterson.
Blalock claims she did not see the shooting, but heard two gunshots.
Hall told investigators Blalock is the one who pulled the trigger.
In his court documents, he told investigators Blalock was angry with Patterson because of an STD and issues at school. He said thought at one point Blalock was "only going to physically assault" her, court records said.
Hall claims while Blalock was hiding under a blanket before picking up the victim, that Blalock had two knives, and followed her instructions because he was afraid of getting hurt.
Court documents show that both suspects said a hunting rifle was used to kill Patterson.