FALL RIVER — Jose Amador-Ayala, who was arrested in the fatal Christmas Eve stabbing of an ex-boyfriend of a woman he was dating, was indicted Thursday by a Bristol County grand jury on a charge of murder.

The indictment transfers the case from District Court to Superior Court, where more serious crimes are prosecuted. Amador-Ayala, 23, has been held without bail since his Dec. 24 arrest on suspicion of murdering 39-year-old city man Gary Werra.

Following his arrest, Amador-Ayala told police he was fixing a boiler with Werra at an Angell Street home on Christmas Eve when the men started arguing over how Werra still lived at that address with Werra’s ex-girlfriend, a woman who at the time of the murder was in a relationship with Amador-Ayala, according to a police report prepared by Detective Derek Beaulieu.

Amador-Ayala, of 1428 County St. Apt. 2, said he “snapped,” took a knife off of a table, and used it to stab Werra repeatedly. After he stopped stabbing Werra, Amador-Ayala told authorities that he checked the man’s pulse, and determined he was dead.

He said he stashed the knife behind a washing machine in the basement and called his sister to ask her to pick him up, then wrapped Werra’s body in trash bags and duct tape, Beaulieu said in the report.

His sister, in an interview with police, said she arrived at the Angell Street residence and saw Amador-Ayala emerge from a basement entrance “dirty and frantic,” according to the report. She said she saw him try to place a laundry bag over an object wrapped in plastic, only realizing the object was a body when a hand tumbled out. She said Amador-Ayala then put Werra’s body in the trunk and told her to drive him somewhere to dispose of it.

Shocked and fearing her brother may harm her, she acquiesced to Amador-Ayala who directed her to Atlantic Boulevard in the area behind Gold Medal Bakery, later telling police that she remained in the car while her brother hauled the body into the woods, according to the report.

She took a picture of the area with her cellphone, which she showed to investigators, the report states. She told police Amador-Ayala said “he had killed Gary and that he was happy about it” while the two were in the car.

Officers found Werra’s body about 5:30 p.m. that Tuesday underneath an old mattress in a remote, wooded area off a dirt path that branches off from Atlantic Avenue, according to police reports. After he dumped the body, Amador-Ayala told his sister to bring him home so he could clean up, the report states. She told police she dropped her brother off at his County Street apartment then drove to her boyfriend’s house and told his family that her brother had killed someone, and her boyfriend’s grandmother called the police.

Police arrested Amador-Ayala at gunpoint outside the Angell Street residence where the stabbing occurred, where police said in a report he went to remove the knife from behind the washing machine. Amador-Ayala had with him two knives covered in apparent dried blood when he was arrested.

Blood was found in the trunk of the car allegedly used to dispose of Werra’s body and in the basement of the Angell Street home where Amador-Ayala and Werra had been repairing the boiler, according to the police report. Amador-Ayala’s bloody clothes were retrieved from Amador-Ayala’s mother’s home.

Amador-Ayala’s Superior Court arraignment is scheduled for March 13.