U.S. soldiers are under investigation following the death of an Afghan commando who was allegedly responsible for an insider attack in October.

The October attack claimed the life of a Czech soldier, Cpl. Tomáš Procházka, who was serving with NATO’s Resolute Support mission to train and advise Afghan forces.

Two other Czech soldiers were wounded in the attack, which took place at Shindand air base in western Afghanistan’s Herat province, according to a press release after the incident.

According to The New York Times, the attacker was arrested within hours by Afghan forces. They then transferred him to NATO custody.

When he was returned to Afghan custody later that night, he had been severely beaten and was unconscious.

He died a short time later, Afghan officials told The Times.

U.S. Army Criminal Investigation Command confirmed to Army Times that it is conducting an investigation into the incident.