EMBED >More News Videos The 18-year-old suspect is being sought by police.

ROSENBERG, Texas -- Rosenberg, Texas police say they need your help catching a "tough guy" who knocked out someone from behind.Investigators said 18-year-old Alejandro Maldonado is wanted for aggravated assault after he was caught on surveillance camera running up on a man and throwing a punch.The force of the hit knocked the 30-year-old victim's baseball cap from his head, and you can see the victim laid out face down on the concrete after the attack.Police said the video is callous and cruel, which is why they are trying to get this video out there so he will turn himself in.Maldonado and the victim were walking out of Ruchi's Mexican Grill when the assault occurred. Police said they do not think Maldonado knew his victim.It appears this might be part of the viral video trend online known as the "Knockout Game," and investigators said they don't want other teens getting any ideas."You think it's a game, your friends might peer pressure you into doing something, and it's a serious offense, it's a felony, it's an aggravated assault," Rosenberg Police Lt. Chad Pino said. "In this case, he sustained some serious injuries, and it's not a game. It's not going to be funny when you're in prison."As Pino said, the victim in this case was severely injured, spending several nights in a nearby hospital.The motive for the attack is not known, but officers said they had spoken to Maldonado last week.Maldonado was going to turn himself in, but ended up cutting off communication with police instead. Now they are hoping the release of the video will force him to come in.The Rosenberg Police Department said your tip on Maldonado's whereabouts could earn you a reward.If you know where Maldonado is, you should call Crime Stoppers at 281-342-TIPS or Detective Mehling at 832-595-3814.