SEATTLE, Wash. – Seattle’s police watchdog agency is investigating the use of pepper spray against protesters.

The protest Monday was largely peaceful but turned chaotic as officers dispersed the crowd using tear gas and flash-bang devices.

Authorities said demonstrators threw fireworks and tried to storm a barricade, but citizen video posted on social media showed the chaos may have actually begun when an officer grabbed a demonstrator’s umbrella across the barricade.

Nearby officers then began spraying chemicals and firing flash-bangs.