Returning a deposit question after murder

[Jason P.]

So I have a duplex and a tenant had 4 friends over and one of the younger ones was playing with a gun and shot his friend in the head and killed him (all early 20’s) unfortunately.   The tenant is moving out because of such a traumatic experience and I am wondering about the deposit.  The place looks clean blood was cleaned off the walls, most was on the couch he threw out.
Do I return the deposit?   I’m just wondering how to navigate renting it out again do you have to disclose a killing in the unit?    

Thanks