Protesters took to the streets of Ferguson, Missouri on Monday evening to peacefully protest on the one-year anniversary of Michael Brown's death, but skirmishes between the crowd and police erupted shortly after 8 p.m., according to the St. Louis County Police Department.

"Frozen water bottles thrown at police. Command to disperse has been given. Those who do not comply are subject to arrest," the St. Louis County Police Department tweeted at 8:16 p.m.

Police began to make arrests as some protesters dispersed. There were about 75 police officers, 150 protesters and 50 reporters at the scene, reports the St. Louis Post-Dispatch.

Demonstrators continued to march and chant despite the fracas. According to the St. Louis Post-Dispatch, around 9:30 p.m. witnesses reported that rocks and bottles were being thrown at police.

"Officers are being hit with rocks and bottles. We continue to support free speech, but agitators who ignore orders to disperse risk arrest," St. Louis County Police Department tweeted at 10:13 p.m.

St. Louis County police report that 23 people were arrested from roughly 9:30 p.m. Monday to 12:15 a.m. Tuesday.

On Monday night, a St. Louis County official declared a state of emergency, citing that violence had impaired demonstrations, reports CNN.

"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.

The executive order placed St. Louis County Police Chief Jon Belmar in command of law enforcement operations in Ferguson and the surrounding areas, Stenger said.

During the day Monday, about 200 demonstrators marched from Christ Church Cathedral to the Thomas F. Eagleton United States Courthouse in St. Louis carrying signs, chanting and demanding the Justice Department take action.

The courthouse demonstration resulted in the arrests of 56 people, St. Louis Metropolitan Police Department spokeswoman Schron Jackson told CNN.

This video was posted to social media on Monday, showing police officers arresting activist and intellectual Cornel West, who was also arrested at an October Ferguson Police Department protest:

Protesters blocked part of Interstate 70 in Earth City by holding hands and forming a line across the highway. Some held yellow signs that read, "Ferguson is everywhere." Roughly 20 minutes after the road block began, troopers walked protesters to the road shoulder. Some unruly protesters were arrested.

Michael Brown Sr. posted a thank you message to Facebook on Monday, "My family and I are truly humbled by the level of support that we received over this weekend. Our marches were all done very peacefully. So please be careful, mindful and protect yourselves from those who would like to see this be unsuccessful."

Monday's protests followed a night of violence on Sunday when gunfire rang out, sending demonstrators and police fleeing, according to CNN.

The alleged shooter, 18-year-old Tyrone Harris of St. Louis, is accused of firing multiple rounds at police with a stolen handgun. Police returned fire, injuring Harris. He is hospitalized in critical condition and in police custody.

Harris has been charged by prosecutors with four counts of first-degree assault on law enforcement, five counts of armed criminal action and one count of shooting a firearm at a motor vehicle, St. Louis County Police Department spokesman Sgt. Brian Schellman said.

He is being held on a $250,000 bond, according to Schellman.

The anniversary vigils of Brown's shooting death had started peacefully Sunday, but by Sunday night, police and protesters had a tense standoff on West Florissant Avenue, not far from where Brown was shot.

Objects were thrown at police, businesses were damaged, and a journalist was attacked and robbed in a parking lot, the St. Louis County Police Department said.

One St. Louis County police officer was struck in the face with a brick, while two others were pepper-sprayed.

"We're ready for what? We're ready for war," members of the crowd chanted.

Police donned helmets and shields and called in tactical units as they pushed crowds back.

The details of Brown's killing by Officer Darren Wilson on Aug. 9, 2014, have caused nationwide focus on what some describe as racial bias by police.