Bad Tenant Question in duplex

[Steve Pavlat]

Hey BP community. I have an upper and lower duplex where the tenants have not gotten along since day 1. More petty arguing back and forth in my opinion. The upstairs tenant asked a couple months back if his friend could move in to help pay rent. I told him yes as long as we filled out an application and added him to lease. He never got back to me so I assumed he never moved in. Fast forward to recently. Upstairs tenant friend has been living there and allegedly got side swiped/hit by downstairs neighbors with car in driveway. Downstairs neighbor called me while yelling at upstairs neighbors. Not sure how to handle a. an alleged accident and b. Tenant friend living there but not on the lease. any thoughts or suggestions? Let cops deal with “accident” if they want to call? Upstairs tenant was moving out by end of month as well. Thanks