The mere presence of a cop, even without a visible weapon, will escalate any situation regarding mentally unstable people. Period.
If you don't understand why a person going through a crisis would freak out when a figure of (ultimately violent) power appears right after they picked a weapon you have a serious problem with basic empathy.
For the record, I haven't had any bad experiences with cops, in fact every interaction I've had so far has been either neutral or actually pretty nice. I've had my fair share of breakdowns as a teenager tho, and I can assure you that a cop would've never helped a single time. Even the nicest one.
Same energy