What started as a peaceful rally for immigrant rights Friday in Seattle quickly descended into violence when a group of suspected anarchists smashed windows and hurled objects at police, who responded by launching tear gas and stun grenades.

Protesters reportedly threw bottles, rocks, and flaming objects at police, in addition to damaging dozens of cars and smashing windows in the Capitol Hill neighborhood of Seattle. At least three officers were hospitalized after sustaining serious injuries in the melee.

Several people reported injuries from tear gas, and at least 16 protesters were arrested following the demonstrations,

The annual protest, called the May Day March for Workers and Immigrant Rights, had received prior clearance from Seattle police to march from Seattle's Central Area to the federal courthouse downtown. An estimated 1,000 people participated in the event, carrying signs that advocated for education, labor rights, Native Americans, solidarity with Baltimore, and a variety of other causes.

The protest was generally peaceful, with police lining the route on bicycles and watching from afar until black-clad members of anti-capitalist and anarchist groups joined in, chanting anti-police slogans and carrying signs against police brutality.

Pepper spray flash bangs craziness. Police took back the street #MayDaySea #Video pic.twitter.com/jY9XF1ANZ7 — Lauren Frohne (@laurenfrohne) May 2, 2015

Video shows people running from tear gas and flashbang grenades as bike cops clad in riot gear use their bicycles to block the street. People with black kerchiefs and masks covering their faces hurled objects at the cops, spray-painted anarchist symbols on store windows, and damaged more than two dozen vehicles. One person burned an American flag in front of a sculpture that was vandalized. Much of the violence took place at Seattle Central College, a community college where protesters burned trash cans and lit fires across the campus.

Getting hectic. Concussive devices being thrown by police. Bottles from the crowd. pic.twitter.com/QDI6J9QDqA — Evan Bush (@evanbush) May 2, 2015

Anarchists light trash cans and sticks in front of Seattle Central #MayDaySea #Video pic.twitter.com/U8IXHT6E3f — Bettina Hansen (@bettinahansen) May 2, 2015

Demonstrators chanted, "no justice, no peace, fuck the police" as officers attempted to quell the commotion.

Seattle Mayor Ed Murray released a statement urging caution and safety.

"Seattle Police are advising that businesses on Broadway and other Capitol Hill streets should take reasonable precautions to protect their employees and customers," the statement read. "Police will continue to work to protect people and property in the area, and will make arrests when necessary."

Calm returned to Seattle on Saturday and police reopened traffic on the main streets.