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A U.S. citizen and Army veteran, Nicholas Maimer, was killed in Ukraine, his uncle confirmed this week.

Maimer, a former Green Beret, previously said he went there to help train Ukrainians in how to defend themselves. In an interview with the Idaho Statesman last year, Maimer said he felt a “calling” to help in Ukraine after Russia invaded. Before the invasion, he had been teaching English in Spain.

“I think this is one of the most clear-cut unjust invasions in recent history,” he told the newspaper. “It’s really obvious to everybody that it’s an unjustified invasion. So I felt like my moral compass just pointed me towards it.”

The nonprofit organization he appeared to be working with in Ukraine said it did not have any verified details about his death.

The Wagner Group, a Russian mercenary company, posted photos of Maimer’s identification cards on Telegram, including his Idaho driver’s license, U.S. Uniformed Services ID and Department of Veterans Affairs ID.

According to his LinkedIn, Maimer retired from the U.S. military in 2018 after more than 22 years.

A State Department spokesman said, “We are aware of those reports of the death of a U.S. citizen in Bakhmut and we are continuing to seek additional confirmation.” The department added that it continues to warn U.S. citizens not to travel to Ukraine due to the armed conflict.

Bakhmut, a city on the front lines in eastern Ukraine, has been the scene of fierce fighting for months, with Ukrainian forces battling to fend off a Russian advance that the Kremlin views as key to its war efforts. Ukraine has recently claimed to be gaining ground.

A CBS News team visited a lookout point near the city in March and spoke with Ukrainian forces involved in the fighting to hold Bakhmut. “If the Russians take Bakhmut then Ukraine will be at a serious breaking point,” said Vladyslav, a member of a tank unit. “It will be hard to get them out of there, and they will have many roads under control, so it will not be possible to bring supplies to our people.”

Imtiaz Tyab, Agnes Reau, Tucker Reals and Olivia Gazis contributed reporting.

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