FERGUSON, United States, Aug. 11 (Xinhua) -- U.S. Federal Bureau of Investigation has opened a civil rights investigation into the shooting of a African American teen on Saturday.

The incident took place in Ferguson, Missouri on Saturday. Witnesses say 18-year-old Michael Brown was shot and killed with his hands in the air.

A vigil for the teenager turned violent on Sunday night as more than 30 people were arrested for vandalism and looting in Ferguson. The situation became so unstable that at one point police used tear gas for crowd control, according to the Associated Press. More than 200 police officers were called in from surrounding areas to assist.

During a Sunday press conference, St. Louis County Police Chief Jon Belmar said Brown and another person attacked the police officer on Saturday afternoon in front of an apartment building in Ferguson. Belmar also said one of the two men reached for the police officer's gun as he was being put in the car. A short fight ensued and Brown started to run. Belmar said the officer fired his gun, hitting Brown, about 35 feet from the car.

But witnesses maintain that Brown, who was scheduled to begin classes at a local college on Monday, was trying to surrender.

The family has hired high-profile Florida attorney Benjamin Crump, the lawyer on the Trayvon Martin case. The 17-year-old African American was fatally shot by a neighborhood watch volunteer in Florida in February 2012.