An annual pillow fight at the U.S. Military Academy turned violent last month, as some freshmen cadets stuffed their pillowcases with hard objects and beat each other unconscious. Altogether, 30 cadets were injured, including 24 who suffered concussions.

The bloody pillow fight took place on Aug. 20 as part of a traditional rite of passage to celebrate the freshman cadets for completing a grueling seven-week training program, said spokesman Lt. Col. Christopher Kasker, according to the New York Times. The event is also a way to build camaraderie.

He added that the cadets were told to wear helmets by the upperclassmen overseeing the fight. However, video and photos of the incident uploaded on social media show that many did not. Rather, some cadets packed their helmets in their pillowcases. As a result, many cadets suffered from busted lips, nose bleeds and dislocated shoulders. At least one person suffered from a broken leg, said cadets who asked to remain anonymous.

"West Point applauds the cadets' desire to build esprit and regrets the injuries to our cadets," said Kasker in a statement. "We are conducting appropriate investigations into the causes of the injuries."

Photos posted on Twitter show freshmen, also known as plebes, with bloody faces and bloody pillows, while at least one person was put into an ambulance.

"My plebe was knocked unconscious and immediately began fighting when he came to," said an unnamed upperclassman on the social media forum Yik Yak, adding "I was so proud I could cry."

"4 concussions, 1 broken leg, 2 broken arms, 1 dislocated shoulder, and several broken ribs. That's one hell of a pillow fight. #USMA19," tweeted a freshman.

"If you don't come back with a bloody nose, you didn't try hard enough," said a male first-year cadet, repeating what his upperclassman commander told him.

The academy said it has no plans to end the annual pillow fight, which has been a tradition since at least 1897.

Watch a video clip of the fight below.