Thank you all for your input! A few updates:

After discussing with the landlords, we've posted warnings at all building entrances, hallways, and around the perimeter of the property. Thankfully there has not been a reported incident since. The cops have made their presence much stronger in recent days, and the apartment company has posted an all night security team at the building for the time being.

Again I appreciate everyones' thoughts, and I agree a discussion of situations would be a valuable resource!