Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

FERGUSON, Mo. — Chaos erupted in Ferguson, Missouri, Sunday night as the city prepared for a state-imposed curfew almost a week after the police-involved killing of Michael Brown, an unarmed 18-year-old. Tear gas, armored vehicles, and flares were being used on demonstrators.

"We kept marching, they started firing tear gas and that's when everybody turned and ran back," said Reggie Edwards, 21, of St. Louis, adding that police fired rubber bullets during the protest. Another protester, Bobby Kalbfell, 27, said he had to help a woman who appeared to be in her 60s flee by placing her on his shoulders. "There was absolutely no provocation," he said.

A police captain told NBC News that a Molotov cocktail may have been thrown behind a strip mall about a half mile from the main protest area, and dozens of police outfitted in riot gear could be seen standing in the parking lot. There was a volley of explosive-like sounds, and a helicopter could be heard buzzing overhead.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

Police told MSNBC's Mike Biette and Bruce Carter that a market was set on fire and that shots were fired in Ferguson, though it was unclear who fired them.

Reports of shots fired at W. Florissant and Solway. Please leave the area immediately! — St. Louis County PD (@stlcountypd) August 18, 2014

Earlier in the evening, hundreds of people lined the avenue where Michael Brown, who was black, was shot to death by a white police officer, and where protesters and police have repeatedly clashed over the last week, triggering Gov. Jay Nixon to institute a state of emergency and President Barack Obama to call for calm.

In the hours before the midnight curfew, authorities were keeping a low-key profile. There were impromptu marches, with people sitting on cars and drivers honking horns — many were waving signs and wearing t-shirts in support of Brown. Justin Winfield, 38, said he would not obey the curfew. "We're ready to go to war with the police," he said.

IN-DEPTH

SOCIAL

Molotov cocktails being thrown at police. Tactical units on scene. Please leave the area! — St. Louis County PD (@stlcountypd) August 18, 2014

Police giving warnings. Moving forward. https://t.co/hNr1AK3THj — Antonio French (@AntonioFrench) August 18, 2014

—Tim Stelloh, Mark Potter, Rob Rivas and Rick Brown