Seattle police clashed with crowds Friday evening as a May Day march moved through the streets and left damage in its wake.
The demonstrations began as a peaceful immigration rally in downtown, but as the rally ended, an anti-capitalist march began moving through the streets.
According to the Seattle Police Department, 15 people were arrested during the protests. Three police officers also were injured, two of whom had to be transported to the hospital.
After violence erupted, the Seattle Police Department called the demonstration a "riot."
The police department also said on Twitter that protesters threw an explosive device.