The schools need to hire more teachers, city hires more police, etc.

Definitely a lawyer letter and possibly a police call.As the listing agent I would be incensed when the owner called me to say the tenant was told that I made a comment that they were being difficult. 

I attended their eviction class last spring and they had many useful speakers - a real estate lawyer, police, as well as a panel of landlords.  

@Michael BowserSo as far as a entry lock to their apartment you are responsible to make sure it's properly working,I wouldn't trust them to do it or expect them to do it right.If if was damaged, then charge them for repair.It's a huge security issue something I personally wouldn't let go 1 day.If they cracked the frame then OMG was it a break in,, did they make a police report,, if not charge them.Cracked frames are not just a put a piece of duct tape on it,could mean a whole new jamb.The extended fix-it metal door jamb things are ok for temp job, but look terrible and is not what was there before.Take photo's, charge them, replace, not repair. 

I realize that the safety of a human being trumps my mortgage payment/bottom line - but am I allowed to ask for a copy of a police report?

Did she file a police report to state an attempted break in?

And contact emergency services of your new phone number, police, fire so they have record of that. 

A month goes by, no issues until tonight- Tenant B says girlfriend threatened to hit her, Tenant B gets police and lawyer involvedAs a landlord, my solution was to ask BOTH guests (not the tenant) to never come back to the house again, or I will evict the respective tenant.  

Is this something that the local police / sheriff serve? 

The police Brandon,you call the police.If your life has been threatened with bodily injury by another person you call the police for help.If you come home and find your stuff all over the front yard and your doors locked and unable to access the property,you have been illegally evicted and you need to call the police and report what happened and get a police report on whatever items are missing and have been stolen.This is a civil matter and you will call a lawyer and sue them in court.