SAN JOSE (CBS SF) — A student at San Jose State University has filed a civil rights complaint against campus police officers who allegedly assaulted him and then placed a bag over his head to stop him from bleeding on the interior of their patrol car.

Alan Chen, now a senior at SJSU, was waiting in line to get into a concert on campus with several friends on April 17, 2015 when one of his friends got involved in an argument with event center staff, according to the complaint filed in the U.S. District Court for Northern California. Chen and his group of friends were escorted out of line by event staff and barred from the concert.

Chen said he was walking away from the event center when he stopped to talk to someone he knew in the back of the line.

Moments later, two people — identified in the complaint as Officers Johnathon Silva and Munir Edais — walked up to Chen and asked him what he was still doing in line. The complaint states that they did not identify themselves as police officers before grabbing Chen by his arms and biceps, and pulling him away from the line.

Then, the two officers hurled Chen to the ground, slamming him into the concrete walkway face-first, the complaint alleges.

Chen was knocked unconscious and his front teeth were shattered.

A third officer — identified in the complaint as Officer Sean Farrell — allegedly stepped on Chen’s back to hold him down while he was unconscious.

The complaint alleges that these three officers punched and physically assaulted Chen as concertgoers watched.

“Many bystanders witnessed the entire encounter and saw the excessive force take place,” the complaint alleges.

Chen was then “dragged” by his handcuffs to a patrol car by Officers Edais and Silva, the complaint alleges.

Chen, bleeding from the mouth, was placed in the back of the patrol car and told not to bleed on the car.

The officers made fun of Chen, saying, “Oh man, look what you did to his face,” and “hey, stop bleeding all over my car,” among other comments, the complaint alleges.

Two other officers — identified as Scott Buckovic and Lee Tassio — who the complaint said watched the situation unfold, allegedly helped Edais place a bag over Chen’s head. The complaint describes the action as causing Chen extreme neck pain and “causing him to choke on his own blood.”

“This was done solely to prevent further bleeding in the police car,” the complaint states.

Chen, still handcuffed, was laying on his side in the police car with the bag over his head when one of the officers allegedly pulled on the bag to force him into an upright position, causing Chen extreme pain, the complaint alleges.

San Jose State University told CBS San Francisco, “This concerns us greatly we will look into it immediately.”

A university spokesperson later added, “Although we’ve just become aware of this legal complaint, the allegations appear to vary materially from our understanding of the facts and/or department policies. We are continuing to review the matter and will respond appropriately in court.”

Chen’s attorney, Steven Berki, told CBS San Francisco that he has obtained a video from a chest-mounted police camera that captured the beginning of the incident including the officers slamming Chen into the ground. A video taken by a person in line for the concert also captured the incident, he said.

Berki said witnesses have also come forward, all describing the incident as inappropriate.

The police report of the incident, Berki said, had no mention of a bag being used.

Placing a bag over the head of someone in custody, often referred to as hooding, is a form of sensory deprivation that is considered by many to be a violation of not only U.S. civil rights, but also international human rights law.

The Santa Clara County District Attorney’s Office did not immediately respond to CBS San Francisco’s inquiry into whether any criminal charges have been filed against the officers listed in the complaint.

Chen was not arrested, but was cited for disturbing the peace and paid a fine, Berki said.

Berki said Chen had to get emergency teeth implants, which he described as an expensive emergency service, after his teeth were broken by the officers.

The incident caused Chen not only physical pain and monetary loss, but also emotional distress, said Berki.

“He’s really upset that it happened,” Berki said, noting that Chen still doesn’t understand why the officers were so aggressive with him.

By Hannah Albarazi – Follow her on Twitter: @hannahalbarazi.