Spc. Joseph J. Nelk, deployed in Ukraine with his New York Army National Guard unit, died on Sunday of apparent natural causes, according to the armed forces.

Nelk, 21, is from Pittsford and enlisted in March 2015. He was based in Niagara Falls and among 220 soldiers who in November took on the mission of training Ukrainian Army troops.

The Army stated that the incident is still under investigation.