Why did 5000 african americans join patriot militias

There were several reasons as to why around 5,000 African Americans joined patriot militias, but the ones that filled the glass was that a couple of fellow African Americans were attacked and killed by the police without any reason for such a thing. This resulted in revolt and anger among the African American population in the United States, so lot of people decided to go out on the streets and look for revenge. They were taking revenge on innocent people though instead of the people that were creating such circumstances. The police and military were sent to stop this and most of those 5,000 people ended up in prison.