NEWPORT BEACH -- A UCLA tennis player from Newport Beach is hospitalized in a coma after family members say he was sucker-punched at a concert.

Jeffrey "Jake" Fleming, 20, attended a Rascal Flatts concert in Texas with friends Saturday when he was attacked by an unknown assailant following the performance, his family said.

Fleming was punched in the face and knocked to the ground, causing bleeding and swelling in his brain.

He remained in a medically-induced coma and was listed in critical condition at Dallas' Baylor University Medical Center as of Wednesday night, according to his family.

Police believe Fleming's group may have been involved in an argument with another group at the concert.

As Fleming and his friends waited for a taxi after the show, a group of men approached and started swinging, police said.

Another person in Fleming's group was also punched but suffered only minor injuries.

Fleming's father, who spoke to two men who were there at the time of the attack, says his son was completely caught off-guard.

He says Fleming had planned to spend his summer teaching tennis and taking classes at UCLA. The family is staying in Dallas until Fleming is well enough to return to Southern California.

Police describe the suspect as a white man, about 20 years old, 6 feet 1 inch tall and about 190 pounds.

It's believed he fled in a white, unmarked party bus with several potential witnesses on board.

Anyone with information is asked to call Dallas police at 214-671-3584 or North Texas Crime Stoppers at 1-877-373-8477.

The family is offering a reward for any information that leads to an arrest.