Rioter (noun)

A person who participates in a riot, a violent and uncontrolled public disturbance.

Origin:

From riot ("to make a loud disturbance") + -er.

Examples:

1. The rioters were arrested and charged with disorderly conduct.
2. The police had to use force to disperse the rioters.
3. He was identified as one of the main rioters in the video footage.
4. The rioter was seen throwing a brick at a police car.
5. The city was on high alert for fear of more rioters.