You must be naive, disingenous, or, frankly, hateful of blacks. Why does "Karen" need to check Mr. Cooper's behavior? She's the one breaking the law.
Now, as for someone getting killed, she knows that reporting that "An African-American man is threatening me" is going to bring out the police in all their "black-male-threat" glory. You're not supposed to die for passing a fake $20. You're not supposed to die for having something hanging off your rear-view mirror. You're not supposed to die for walking down the freakin' street minding your own business, but, unfortunately, BLACK MEN DO.
I'm glad I don't know you. Begone and trouble me no more. Shalom and Salaam.