If that fucker calls back, record it in some fashion and report that shit to your nearest police station right away.
I dealt with something similar - some fuckwit muslims woke me up one afternoon while I was asleep and threatened my life. The calls came from the next municipality over. Took it to the police station twice before the attending officer called back the number and told'em off, never heard back from the fuckers since.
May have been a prank call, got a few couple years ago, like 3 in a row from different numbers, all of them threatening me with something. Eh, just blocked and moved on with my life X3
Call the police if you had saved that stranger's phone number?
I dealt with something similar - some fuckwit muslims woke me up one afternoon while I was asleep and threatened my life. The calls came from the next municipality over. Took it to the police station twice before the attending officer called back the number and told'em off, never heard back from the fuckers since.