Autopsies show the three U.S. Marines found dead in a parked car at a gas station in a coastal North Carolina community over the weekend died from carbon monoxide poisoning, the Pender County Sheriff's Office said Wednesday.

"I am saddened by the timeless and tragic death of these three young men, who served our country honorably. Our thoughts and prayers remain with their families and colleagues during this time," Sheriff Alan Cutler said in a statement.

The Pender County Sheriff's Office said deputies were responding to a report of a missing person when they found the three Marines early Sunday at a Speedway convenience store along a highway in Hampstead, North Carolina, about 30 miles south of Marine Corps Base Camp Lejeune.

A woman called the office that morning indicating that her son, a Marine, had failed to arrive on a flight in Oklahoma the night prior, the sheriff's office said.

"The caller indicated that she had spoken with a supervisor in his unit and that someone was enroute to the location to see if they could locate the missing person," the office said.

The woman knew to direct deputies to the gas station because she had pinged her son's phone to find its location, according to Sgt. Chester Ward, spokesperson for the sheriff's office.

At the time, sheriff's deputies were also working on a separate missing person report, the office said.

The office said it received a second call later that morning indicating the missing person had been located at the Speedway and that he, along with two other Marines, were deceased inside of a car.

Who are the Marines who died in North Carolina?

The U.S. Marine Corps identified the three men as Marine Corps Lance Corporal Tanner J. Kaltenberg, 19, from Madison, Wisconsin; Marine Corps Lance Corporal Merax C. Dockery, 23, from Pottawatomie, Oklahoma; and Marine Corps Lance Corporal Ivan R. Garcia, 23, from Naples, Florida.

The men were motor vehicle operators with the Combat Logistics Battalion 2, Combat Logistics Regiment 2 and 2nd Marine Logistics Group at Camp Lejeune, according to First Lt. Raymond Fullbright, of the 2nd Marine Logistics Group.

The North Carolina Office of Medical Examiner performed the autopsies Wednesday, the sheriff's office said.

Ward said he did not know how long the car had been parked at the gas station before it was found or if there were any problems with the car. He said he also did not know where the Marines were headed.

The families of the three Marines did not immediately respond to requests for comment.

Who was Merax Dockery?

The youngest of five siblings, Dockery grew up in Seminole, Oklahoma, and graduated from Seminole High School in 2019.

"Our condolences and prayers are extended to his family and friends," said Bob Gragg, Superintendent of Seminole Public Schools, in a statement.

Dockery entered active-duty service in June 2020, according to the U.S. Marine Corps. He was previously based in San Diego at the Marine Corps Recruit Depot, at the School of Infantry-West at Camp Pendleton in California and in Missouri at Fort Leonard Wood.

His military awards include the National Defense Service Medal, Navy Meritorious Unit Commendation and Global War on Terror Service Medal.

Dockery’s mother, Heather Glass of Maud, Oklahoma, told the Associated Press her son joined the Marines "for personal growth" and so that he could travel, with the possibility of making the military a career.

Glass said she and another relative had driven to the Oklahoma City airport Saturday evening to wait for her son who was slated to fly home for his grandfather's funeral. When he didn’t arrive, Glass' daughter started calling North Carolina hospitals and jails while Glass contacted the sheriff’s office and her son’s sergeant at Camp Lejeune, resulting in a search.

"I feel at peace because I know he was asleep when he passed," Glass told the AP.

Several of Dockery's family members shared photos and messages on social media in recent days.

"My handsome kind baby brother is gone," one of Dockery's sisters, Micah, wrote in a Facebook post. "I don’t feel like this is real, it can’t be."

Who was Tanner Kaltenberg?

Kaltenberg attended Verona Area High School in Verona, Wisconsin, and played baseball and hockey, according to local news reports from the time.

He entered active-duty service in May 2021, according to the U.S. Marine Corps. Before Camp Lejeune, he was based in San Diego at the Marine Corps Recruit Depot and in Missouri at Fort Leonard Wood.

Kaltenberg's military awards include the National Defense Service Medal, the Sea Service Deployment Medal, the Navy Arctic Service Ribbon, and the Global War on Terror Service Medal.

Who was Ivan Garcia?

Garcia graduated Lely High School in Naples, Florida, in 2019.

"It is a sad day anytime one of our Collier County Public Schools alumni passes away, especially at such a young age," said Chad Oliver, spokesperson for the school district.

Garcia entered active-duty service in July 2019, according to the U.S. Marine Corps. Before Camp Lejeune, he was based in San Diego at the Marine Corps Recruit Depot and in Missouri at Fort Leonard Wood. He was also based at the Corps Recruit Depot Parris Island in South Carolina.

His military awards include the National Defense Service Medal, Navy Meritorious Unit Commendation and Global War on Terror Service Medal.

Rosely Garcia, who identified herself on Facebook as Garcia's aunt, shared photos of Garcia throughout his life — as a child, with a skateboard, surrounded by family, in uniform and more. Writing in Spanish, Garcia said she could not believe her "beautiful child" is no longer here.