Take matters into your own hands. Unadvisable if theyve threatened to kill everyone. If you can maybe get a recording of them threatening the safety of other tenants you can bring evidence to your landlord, the police.

Raise hell with your landlord after collecting some evidence, id bet your lease has noise regulation. Id also wager you can enlist the help of your neighbors and complain to the landlord together en masse. Pressure that more than one tenant is displeased and might vacate will get their attention.