Discuss as:

Soldier who hit colleague with wooden mallet is disciplined

An online video showing a U.S. soldier hitting a soldier of a lower rank in the chest with a wooden mallet has prompted shock and outrage -- and, ultimately, disciplinary action.

The incident took place in April 2012 at Fort Bragg, N.C. The video shows a sergeant first class striking Sgt. Phillip Roach, 22, slamming him into the wall behind him.

Roach stumbles and then collapses to the floor, hitting his head on a nearby chair. The video ends there, but Roach's father says that after the camera stopped rolling, his son suffered a seizure.

Why would Roach stand quietly by as a fellow soldier slams a large wooden object into his chest? It is actually an extreme version of a promotion ceremony tradition.

When a soldier is promoted while wearing his or her BDUs (camouflage uniform or fatigues), the new rank insignia is a small patch attached to the uniform with Velcro. Often the person "pinning on" the new rank will slam the patch on or even punch it with their fist. (Most of the time this draws laughter or applause and is meant to be funny.)

It isn't sanctioned but it is common.

A U.S. Army spokesperson issued a statement saying, "Corrective action was promptly taken in this case. The 82nd Airborne Division took administrative action against a Soldier involved in striking another Soldier in April 2012 and he was punished under the Uniform Code of Military Justice. The very foundation of what we do depends on trust, and trust depends on the treatment of all Soldiers with dignity and respect by fellow Soldiers and leaders."

A Fort Bragg spokesperson told NBC News that this event was “not in keeping with military service."

The soldier will be fined, receive an administrative punishment and will receive a letter of reprimand in his permanent file. He must also write an apology letter and will be relieved of his responsibilities.

This is a career-ending punishment.

Roach has returned to work as a paratrooper at Fort Bragg, but the spokesperson could not say whether he is back to full duty or whether injuries are preventing him from his duties.

More content from NBCNews.com:

Follow US News from NBCNews.com on Twitter and Facebook