A 22-year-old former U.S. Marine was killed alongside Ukrainian forces in the war with Russia, his relatives told news outlets, in the first known death of an American citizen fighting in Ukraine.

Willy Joseph Cancel was killed Monday while working for a military contracting company that sent him to Ukraine, his mother, Rebecca Cabrera, told CNN. Cancel had recently worked as a corrections officer in Tennessee and previously served in the Marines from 2017 to 2021, joining the Corps the same year he graduated from high school.

Cabrera said her son had signed up to work with the private military contractor shortly before fighting began in Ukraine on Feb. 24. She told CNN he agreed to go to Ukraine.

“He wanted to go over because he believed in what Ukraine was fighting for, and he wanted to be a part of it to contain it there so it didn’t come here, and that maybe our American soldiers wouldn’t have to be involved in it,” she said.

Cancel had volunteered with his local fire department in New York as a high school student, and he had a 7-month-old son, according to an online fundraising page set up by a man identifying himself as his father.

The U.S. government said it had seen reports about the death but did not have official confirmation, according to White House press secretary Jen Psaki.

“It’s very sad. He left a little baby behind,” President Joe Biden said.

Psaki reiterated warnings against U.S. citizens traveling to Ukraine.

“We know people want to help, but we do encourage Americans to find other ways to do so rather than traveling to Ukraine to fight there,” she said. “It is a war zone.”

The State Department also said it was aware of the reports and was “closely monitoring the situation,” but could not comment further “due to privacy considerations.” It, too, urged U.S. citizens not to go to Ukraine.

Cabrera said her son’s body has not been found.

“They are trying, the men that were with him, but it was either grab his body or get killed, but we would love for him to come back to us,” she said.

She said her son flew to Poland on March 12 and entered Ukraine shortly after, to fight alongside men from a number of countries.

A roommate who lived with Cancel in Kentucky in the months before he left for Ukraine said he became interested in going to help shortly after the war began.

“Right around when it was getting serious was when he said he wanted to go,” 21-year-old Triston Mannahan said. “He felt obligated because that (the war) was wrong and he wanted to help.”

Mannahan said Cancel packed his things over a couple of days in mid-March and left for Europe.

“He’s really brave,” Mannahan said. “That’s what he wanted to do.”

The fundraising page said Cancel’s wife got a call Tuesday informing her of his death. The father wrote that Cancel decided to go to Ukraine because he wanted to defend innocent people.

Cancel graduated from Newburgh Free Academy in New York in 2017, the school district said. An instructor who mentored him in the Air Force Junior Reserve Officers’ Training Corps, Master Sgt. Christian Granda, said he was a “dedicated cadet who served our community well” and joined the Marines right after high school.

Cancel worked at a private prison in Tennessee from May 2021 until January, said Matthew Davio, a spokesman for the private prison company CoreCivic. The Trousdale Turner Correctional Center, a medium security facility, is about an hour northeast of Nashville.

“As a correctional officer, Mr. Cancel served his state and his community by helping maintain a safe, secure environment where inmates can participate in life-changing reentry programs,” Davio said in a statement.

While in the Marines, Cancel served as a rifleman and was stationed at Camp Lejeune, North Carolina. He was given a bad conduct discharge after he was convicted of violating a lawful general order, Marine Corps spokesperson Maj. Jim Stenger said.

He had no war zone deployments, Stenger said. No other details on the bad conduct conviction were provided.

Cancel’s widow, Brittany Cancel, told Fox News that she sees her husband as a hero.

“My husband did die in Ukraine,” Brittany Cancel said. “He went there wanting to help people, he had always felt that that was his main mission in life.”

She said her husband aspired to be a police officer or firefighter.

“He had dreams and aspirations of being a police officer or joining FDNY,” she told Fox. “Naturally when he found out about what was happening in Ukraine, he was eager to volunteer.”

Tens of thousands of Ukrainians are believed to have been killed in the war. Other noncombatants from the U.S. have been killed, including a documentary filmmaker who was slain when his vehicle came under fire at a checkpoint and a man killed while he was waiting in a bread line.