St. Louis County, Mo. has issued a state of emergency following a spate of violence amid protests marking the one-year anniversary of the death of Michael Brown.

“In light of last night’s violence and unrest in the City of Ferguson, and the potential for harm to persons and property, I am exercising my authority as county executive to issue a state of emergency, effective immediately,” St. Louis County Executive Steve Stenger said in a statement obtained by FOX2.

Stenger said Police Chief Jon Belmar will have the authority to “exercise all powers and duties necessary to preserve order, prevent crimes, and protect the life and property of our citizens.”

Two instances of gun violence broke out Sunday night as protesters commemorated the death of Brown, an unarmed black man shot by a white police officer. One of the incidents allegedly involved a gunman firing at a group of police in an unmarked fan. Cops returned fire and the suspect is currently in critical condition in the hospital.

The father of the suspect who was shot called the police version of events "a bunch of lies." He said two girls who were with his son told him he was unarmed and had been drawn into a dispute involving two groups of young people.

Police, protesters and people who live and work in the St. Louis suburb were bracing for what nightfall might bring following more violence along West Florissant Avenue, the same thoroughfare that was the site of massive protests and rioting after Brown was fatally shot last year in a confrontation with a white Ferguson officer.

"Of course I'm worried," said Sandy Sansevere, a retired health care worker who volunteers at the retail store operated by the nonprofit group I Love Ferguson, which was formed after Brown's death to promote the community. "What scares me are the guns."

“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,” Stenger said in the statement. “The time and investment in Ferguson and Dellwood will not be destroyed by a few that wish to violate the rights of others.”

Protests spilled outside of Ferguson. Almost 60 protesters were arrested around midday Monday for blocking the entrance to the federal courthouse in downtown St. Louis. Authorities planned to release them on a promise to appear later in court.

Among those arrested was scholar and civil rights activist Cornel West.

Gov. Jay Nixon agreed, saying in a statement that such "reprehensible acts must not be allowed to silence the voices of peace and progress."

Some protest groups said police were too quick to go into riot mode. Others questioned why plainclothes officers were part of the patrol.

"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 of Black Struggle.

Belmar said it is common to use plainclothes officers. In addition, there were more than 100 uniformed officers from the Missouri State Highway Patrol and the Ferguson and St. Louis County police departments.

Some protest leaders worried about how the latest police shooting — especially on a day honoring Brown — could escalate tensions.

"It changes the equation," said Rebecca Ragland, an Episcopal priest who was part of a group that marched to the federal courthouse in St. Louis. "The way the police will respond now will be much more militaristic. It legitimizes a response from the police that's a lot more aggressive."

John Gaskin III, a member of the NAACP national board from St. Louis, was more hopeful.

"I don't believe there will be looting or rioting," he said. "That's not in my vocabulary. We have to have some faith."

The Associated Press contributed to this report.