A strong police presence and rain might have deterred further violence from taking place on what had already become an ugly May Day.
Seattle police made at least a dozen arrests after protesters, including a group of anarchists known as the "black bloc" incited violence against police officers and caused property damage throughout downtown.
While one group gathered at Westlake Park, the March for Immigrant and Worker rights, marched peacefully from the Central District neighborhood to downtown.
Juan Jose Bocanegra, an organizer of the immigrant rights events had said anyone planning violence should stay away.
But black-clad protesters using sticks and bats smashed stores and automobile windows during May Day demonstrations that turned violent in Seattle.
At the federal appeals court building, an FBI evidence team arrived after protesters shattered glass doors with rocks and threw or shot a smoke bomb toward the lobby. The device hit the only door that didn't break, spun off into some nearby bushes and started a small blaze that quickly burned itself out.
Clashes with police continued to escalate during the afternoon. Demonstrators used sticks, smoke bombs, paint, hammers, rocks, and tire irons to do serious damage to businesses and cars.
The mayor issued a special order allowing police to confiscate makeshift weapons. By Tuesday night, police had seized about 70 such items, including one with at least a dozen cigarette lighters taped together.
Seattle Mayor Mike McGinn said many of the most violent protesters, those who had caused damage with rocks, hammers and tire irons, tried to hide in the larger crowd early Tuesday afternoon by shedding their all-black clothes.
Police said some of the property damage included broken windows at American Apparel and Niketown, Bank of America on Olive, Wells Fargo on 4th Ave, the courthouse, cars in the 1500 block of 6th Ave and in the 500 block of Seneca, Homestreet Bank on 6th Ave.
"There's a bunch of smoke, Anarchists,and protesters walking down the street hitting our windows with hammers. Right now, all of our windows are severely cracked or they're about to break. You can hear them cracking," an employee of American Apparel told 97.3 KIRO FM's Dori Monson Show during the activity on Tuesday.
Warning: Video contains some graphic language.
The violence triggered a lockdown at City Hall and caused all downtown Wells Fargo branches to close ahead of schedule.
While trouble continued downtown, the annual May Day March for Immigrant and Worker rights started from Judkins Park to downtown Seattle at 5:00 p.m. (the rally at the park started at 3:30 p.m.) That gathering was described as much more peaceful according to 97.3 KIRO FM reporter Josh Kerns.
"We appreciate that the vast majority of people out there are peaceful participants," McGinn said. "What we know from WTO previously is you get a group of people committed to cause damage...My direction to police is I expect them to respond to law breaking swiftly and aggressively."
Seattle police Sgt. Sean Whitcomb said the department's concerns of violence were real.
"I think we handled it as best we could," Whitcomb said late Tuesday night. "These were, for the most part, peaceful demonstrations. It's such as shame that such a small group of individuals were able to hijack the event and dilute the message to one of violence. They came here and they smashed it up."
People or businesses who had their property vandalized in the May Day demonstrations should call Seattle Police at 206-625-5011 or file a report online.
The Associated Press contributed to this report.
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