actually, you should need enough proof to show the stranger made those remarks, yeah?
like, people make false accusations all the time. like... how many times have karens called the cops wanting exactly this to happen?
Edit to clarify: you need to satisfy a cop that the subject actually represents a persistent threat. That cop then can issue a protective order of a relatively short duration (days, typically), while the courts decide-adversarially- if it is indeed warranted.