A soldier who should've been firing blanks hit an Apache helicopter with live rounds last week during training at Fort Irwin, California, an Army spokesman confirmed on Tuesday.

The soldier, with 1st Battalion, 17th Infantry Regiment, out of Joint Base Lewis-McChord, Washington, was augmenting the 11th Armored Cavalry Regiment for the exercise, Fort Irwin spokesman Ken Drylie said. The cavalry regiment provides opposing-force personnel for rotations at the National Training Center.

The incident took place Friday, Drylie confirmed, and was reported two days later in a post on the U.S Army W.T.F! Moments Facebook page, which included a photo reportedly of the Apache in question.

Army investigators are attempting to determine how the soldier — his name and rank weren't released — came in possession of live ammunition. The OPFOR unit is not issued live rounds, Drylie said.

"That's the $100 question right now, because that unit shouldn't have had live ammo," he said. "So, wherever it came from, they're going to figure out where it came from."

The Apache, with JBLM-based 4th Squadron, 6th Cavalry Regiment, suffered superficial damage from "about four rounds," Drylie said. It landed at 8:44 a.m. as part of a full stop of the training exercise, standard operating procedure when live rounds are introduced unexpectedly. Training resumed later that day after a "100 percent inspection," Drylie said.

The inspection found one live round remaining in the soldier's weapon, he said. The weapon had a blank-fire adapter, but it was blown off by the first live round. The sound of subsequent live rounds led someone to call for a cease fire, Drylie said.

Army Criminal Investigation Command "found nothing criminal in nature" in its investigation of the incident. CID spokesman Chris Grey said via email. Drylie said the soldier's home unit was conducting its own 15-6 investigation into what he called a "quite rare" mishap.

"Accidents do happen and mistakes are made; Army training is by its very nature dangerous," he said. "We take every precaution we can to make sure things don't go wrong, and when they do, we stop and we take a hard look ... and try to avoid making similar mistakes in the future."