State police say 25-year-old Francis L. Giannelli of Glastonbury, a lab technician with no criminal history, turned himself in Tuesday and confessed to emptying his .380 caliber pistol into a pickup truck in Preston early Saturday, killing its passenger, after an earlier altercation at Mohegan Sun.

He was charged with murder, criminal use of a firearm and carrying a pistol without a permit and ordered held in lieu of $1 million. By late Wednesday, he had appeared in Superior Court in Norwich and was taken to a state prison, where he was expected to be placed in protective custody and on suicide watch.

Information about the case is contained in a probable cause report written by state police Detective Robert J. Carey and submitted to the court.

The victim, 35-year-old Robert Thompson of Preston, died of a single gunshot wound to the neck, according to the state Office of the Medical Examiner, which ruled his death a homicide.

Giannelli walked into the Montville Police Department at 7 p.m. Tuesday, saying he would like to turn himself in and confess to the shooting, according to the report. Detectives from the Eastern District Major Crime Squad drove Giannelli to Troop E in Montville and interviewed him for several hours. They took a written statement and took him into custody.

Two state troopers and seven judicial marshals were in court Wednesday afternoon as Giannelli was arraigned before Judge Nuala Droney. Wearing an orange prison jumpsuit, he stood with Public Defender Jean Park and said nothing as the judge read him his rights, set his bond at $1 million and ordered that he be placed on suicide watch and in protective custody in prison.

No members of Giannelli's family or the victim's family were in the courtroom for the brief proceeding. The case was transferred to the New London court where major crimes are tried and continued to Nov. 18.

According to the report, a witness called 911 at 1:22 a.m. Saturday and said he had just witnessed what he believed to be a shooting at the intersection of Routes 12 and 2A. The caller, who is not identified in the report, said that as he turned right onto Route 2A from Route 12, he saw four cars lined up on the eastbound side of Route 2A at a red light. He said a black pickup was in the far right turn lane and there were two light-colored sedans and a third, "sleek"-looking sedan behind them. He said he heard five to seven gunshots from one car into another as he continued driving west and saw the "sleek" car pass the other cars. He said he looked into his rearview mirror and saw the car, which had a Connecticut license plate, making a U-turn and speeding west on Route 2A toward Interstate 395.

At 1:28 a.m., Ledyard police Officer Gary Butters, who was conducting speed enforcement about 6.5 miles away on Route 12 near Inchcliffe Drive, pulled over the black pickup truck, noting the driver's door window and rear window area had been "smashed out." The driver said the passenger, who was unconscious and bloodied, had been shot, and Butters escorted the truck to Lawrence + Memorial Hospital.

At the hospital, the man who accompanied Thompson, identified by state police only as Witness 2, told Butters he and the victim were stopped at the red light when "an unknown person occupying an unknown vehicle" shot several rounds at the pickup, one of which hit Thompson.

Thompson had a single gunshot wound on the left side of his head, just below his ear. He was pronounced dead at 2:14 a.m.

Detectives tracked down the owner of the "sleek" vehicle, which was a 2010 Mercedes Benz C300, and went to his home, where they said "Witness 3" told them he'd had dinner at Mohegan Sun with friends, but refused to speak with them further when they asked for specifics.

In his interview with detectives, Giannelli said the person identified as Witness 3 had picked him up in Glastonbury and they drove to Mohegan Sun. Giannelli said he saw Thompson in the Comix Roadhouse bar, where it looked as if Thompson was taking pictures of him with his cellphone. He said he gave Thompson a look and may have said something to him that Thompson didn't hear.

Giannelli said he ran into Thompson again in the side foyer of the casino and had an altercation with Thompson and the man Thompson was with. He said they exchanged words, and security staff asked them to leave. He said a second altercation occurred before they left because he saw the victim taking pictures of him again.

Giannelli said they ran into one another again on the top level of the Riverview Parking garage, and that as Thompson and the other man got into a pickup truck, they both made "a gun gesture" with their fingers, which he understood to be a threat that they were going to shoot him.

Giannelli said he was in the passenger seat of the car as it pulled up to the stoplight at Routes 2A and 12. He said he looked to his right and saw Thompson and the other man in the pickup truck. He said he was carrying a semi-automatic handgun that night that is not registered to him and that he didn't have a valid pistol permit.

Sitting at the traffic light, Giannelli said he saw the driver, who was older, move his right hand from the steering wheel down to his side and it appeared he might be reaching for a gun.

"Giannelli stated he didn't wait to see what he was reaching for, and shot first," the report says. "He shot six times, emptying his gun, but did in self defense. He never saw the older gentleman display a gun, and stated he probably shouldn't have shot at him, but did in self defense. He didn't remember what the bullets hit, or if he hit anybody at that time."

After the shooting, Giannelli said the pickup truck took a right and his companion made a U-turn and they headed back down the highway in the opposite direction and drove to Middletown.

k.florin@theday.com