FERGUSON, Mo. (AP) — Authorities say at least two people were shot and 31 were arrested in clashes last night in Ferguson, Missouri, where an unarmed black 18-year-old was shot and killed by a white police officer ten days ago.

Protesters filled the streets after nightfall Monday, and police say bottles and Molotov cocktails were thrown from the crowd and that some officers had come under heavy gunfire. Officers fired tear gas and flash grenades.

Capt. Ron Johnson of the Missouri Highway Patrol says "a dangerous dynamic" is developing at night in Ferguson. He's urging protesters with peaceful intent to demonstrate during the daytime hours.

The National Guard is in the area but keeping its distance for now.

Attorney General Eric Holder plans to travel to Ferguson tomorrow to meet with FBI and other officials carrying out an independent federal investigation into the death of Michael Brown.