I'd've called the front desk when they were screaming at each other in the room. The front desk handles this sort of thing more than you and would have a better feel as to whether (for example) these are regular customers, how the local cops react, whether this is a normal or irregular occurrence for the area, etc. If the front desk or the cops had then stopped by the room with a noise complaint, that may have interrupted the disagreement enough that it may not have escalated later on. If they didn't stop by with a noise complaint, I very likely would have done the standard 'banging on the wall to get them to shut up' thing, which may have had the same effect (I have trouble sleeping and this nose would've made me very irritable). I don't know if I'd've opened my hotel room door, but I'd've at least looked out the peephole to assess the situation - and I'd've double-checked the lock and chain on the door during the first argument.