A 17-year-old Indiana high school student murdered two teens last week in a drug deal gone awry, prosecutors alleged Monday.

Connor Kerner, 17, was charged Monday with two counts of murder for fatally stabbing 19-year-old Molely Lanham and her 18-year-old boyfriend, Thomas Grill, after Grill tried to “rob him” during a drug deal in his grandparents’ garage, according to a probable cause affidavit filed by the Porter County Prosecutor’s Office.

“I did something really bad,” Kerner allegedly told two friends last Monday, the day after the couple was reported missing. “I killed someone, and I killed an innocent girl.”

Authorities say the two friends, who have not been identified, told the Cedar Lake Police Department on Friday that Kerner killed the teen couple—who were reported missing by family on Feb. 26—and revealed the approximate location of their bodies and car.

The witnesses told authorities that they came forward despite the drug dealer’s threat to “kill them and their family” if they gave him up, the affidavit said.

Kerner, a current student at Valparaiso High School, is being held without bond at the Porter County Jail after he was arrested on Saturday night. It was not immediately clear if he has a lawyer.

“I want to send my sincere condolences to Thomas Grill and Molley Lanham’s families on the tragedy they are now facing with the heinous death of their children,” Porter County Sheriff David Reynolds said Monday.

According to the court documents, Kerner told Grill to meet him at his grandparents’ home—which is about an hour outside of Chicago—to pick up drugs.

Since his license had been suspended, Grill hitched a ride from Lanham, who drove a black Honda Civic and was waiting in the car during the deal, the affidavit said,

Kerner allegedly told his friends that inside the garage, Grill tried to rob him and a struggle ensued. The 17-year-old allegedly shot Grill when he turned around, missing him the first time.

“Grill fell to the ground and was begging for his life,” according to the arrest warrant. “Kerner advised that he panicked due to being out of bullets in the gun. Kerner then beat [Grill] with a pipe wrench until he died.”

The high school student went outside to find Lanham still in her car, prosecutors allege, and told her to come into the garage. After showing the 19-year-old her boyfriend’s body, Kerner “informed her he was going to let her go, but if she told, he would kill her,” according to prosecutors.

“When she turned to leave the garage, Kerner shot her in the head, killing her,” according to the charging documents.

Scrambling to clean up the crime, Kerner drove Lanham’s car into the garage, loaded the two bodies into the trunk of the Honda Civic, and drove about two miles away, he allegedly told his friends.

In “a field in rural Hebron,” Kerner lit the car on fire with “3 propane cylinders and 3 bottles of 'tiki' fluid” before walking back to his grandparents house “through the woods.”

“Kerner told [his friend] that he had done this before and knew how to cover up a murder and get away with it,” prosecutors allege.

Porter County sheriff’s officers found the vehicle on Saturday, while searching for the missing teens.

“Two heavily burnt bodies, skull fractures to one and an apparent gunshot wound to the head of the other” were found inside the car, the sheriff’s office said. While the identities of the bodies have not been confirmed “all evidence obtained at this point at the scene and through statements given, point to the individuals being Thomas Grill and Molley Lanham.”

Hours later, Kerner was taken into custody.

“This is a heartbreaking loss for HCSC and the entire community. Molley was involved in soccer and track. Thomas was involved in the building trades. They will be sorely missed,” Hanover Community Schools Superintendent Mary Tracy-MacAulay said in a statement Monday.

Grill and Lanham’s family could not be immediately reached for comment.