CNN

A day of peaceful vigils to mark the one-year anniversary of Michael Brown’s shooting death turned ugly late Sunday when protesters threw rocks and bottles at officers, and police critically injured a man who they say fired at them.

The unidentified man in his 20s was undergoing surgery early Monday.

He unleashed a “remarkable amount of gunfire” against the officers using a stolen handgun, St. Louis County Police Chief Jon Belmar said.

“We cannot continue, we cannot talk about the good things that we have been talking about, if we are prevented from moving forward with this kind of violence,” he said.

Belmar said those resorting to violence are not protesters.

“Protesters are people who are out there to effect change,” he said. There were “several people shooting, several rounds shot.”

Peaceful vigil, then chaos

The anniversary observations of Brown’s shooting death by a white Ferguson police officer started off peacefully Sunday.

Throughout the day, vigils honored the unarmed black teen. Attendants observed 4½ minutes of silence to signify the 4½ hours Brown’s body lay on the street after he was shot last year.

PHOTO: People come to the aid of a distraught woman after gunshots were fired near a protest in Ferguson, Mo., Sunday, Aug. 9, 2015.

But the suspect’s gunfire shifted the focus Sunday night.

When officers first saw him, he was running away after allegedly exchanging gunfire with an unknown person.

Some gunfire rang out as reporters were talking to Ferguson’s acting police chief, Andre Anderson. A startled Anderson continued speaking, with a steady burst of gunfire heard in the background. Crowds scattered.

Detectives in an unmarked SUV turned on its emergency lights and pursued the suspect, only to be shot at, according to Belmar. The bullets hit the vehicle’s hood and windshield several times, Belmar said.

As the detectives got out of the car, the suspect allegedly turned around and fired again.

Then he ran toward a fenced area, where he continued firing — until officers struck him multiple times, Belmar said.

The four plainclothes officers involved in the shooting have between six to 12 years of experience, he said. They have been placed on administrative leave.

Night turns tense

By then, police presence had turned heavy, and rumors about the shooting flew.

Police and protesters faced off in a tense standoff on West Florissant Avenue, not far from Canfield Drive, where Brown was shot.

Several objects were thrown at police and some businesses damage read more