A state of emergency has been declared in Ferguson, Missouri, following a night of violence and gunfire that erupted at a demonstration to commemorate the death of Michael Brown.

Protesters from around the country flocked to the St. Louis suburb on Sunday to remember the one-year anniversary of the death of Michael Brown and to demand justice. The unarmed African-American teenager was fatally shot in Ferguson on Aug. 9, 2014 by a white police who was never indicted. The incident sparked a string of national protests, ongoing discussion about race in America, and a number of police reform measures across the county.

Although Sunday began as a day of peaceful protests, it turned into a night of chaos and violence, after people opened fire at a demonstration. One of the suspects involved in the shooting, 18-year-old Tyrone Harris of St. Louis, was then shot and wounded by St. Louis County police officers. He was reportedly in critical condition as of Monday, reports the New York Times.

According to Chief Jon Belmar of the St. Louis County Police Department, gunfire erupted when rival groups began shooting at each other on the west side of West Florissant Avenue, right in the middle of the Ferguson protests.

Four plainclothes officers say they drove their unmarked SUV towards Harris with the car's interior lights flashing, but Harris responded by shooting at the officers, striking their vehicle several times. The police returned fire from inside the vehicle and then chased him down on foot, reports ABC News. Harris was shot mulitple times.

The St. Louis County prosecuting attorney's office on Monday charged Harris with assault of a police officer in addition to nine other counts.

In light of the overnight violence, a top county official declared a state of emergency on Monday. A small group of protesters were also arrested Monday at a federal courthouse in St. Louis.

"The recent acts of violence will not be tolerated in a community that has worked so tirelessly over the last year to rebuild and become stronger," St. Louis County Executive Steve Stenger said in a statement, according to CNN.

Overnight unrest created "the potential for harm to persons and property," the statement said. Stenger added that under the executive order, Chief Belmar will be in charge of police operations in Ferguson and the surrounding areas.

Video posted to social media showed police officers arresting several prominent protesters at the federal courthouse, including activist and intellectual Cornel West.

Gov. Jay Nixon released a statement Monday, stating that the violence represented "a sad turn of events."

The Ferguson Action Council, a coalition of local protest organizations, criticized officials for sending plainclothes officers without body cameras to police the protests.

"After a year of protest and conversation around police accountability, having plainclothes officers without body cameras and proper identification in the protest setting leaves us with only the officer's account of the incident, which is clearly problematic," said Kayla Reed, a field organizer with the Organization for Black Struggle, in a statement on Monday.