What is the reason for these riots?

They were sparked by the mistreatment of an african american man by the name of george floyd. He lived in minneapolis and he was at a store and supposedly tried to purchase something with a “counterfeit” $20 bill. (we aren’t sure if it’s real or not) and someone called the police. the police got him out of his car and he didn’t resist arrest but they were still very aggressive because of the negative stigma that black people have on them. a white minneapolis police officer named derick chauvin presses his knee against floyd’s neck for 9 minutes. a stander by got a video of it and posted it and it went viral. we later figured out that floyd died because of the illegal mistreatment that the cop put him through. all 4 officers involved have been sent to jail and have bails set at over 1 million dollars. this video made people fed up with the way people were treating blacks and they tried peaceful protesting around the country. bad people took advantage of the situation and started looting stores and injuring people. they lit the minneapolis 3rd police precinct on fire. it’s a pretty bad situation.