"Linked to," "suspect," etc. etc. might have suggested she was a dangerous person. Or it might merely suggest she had acquaintance with some less than savory people. Her brother's death was treated as an accident.
Accidents happen and/or murders get treated as accidents sometimes.
Now exactly what psychological test would have predicted she might shoot colleagues in what was apparently a tenure dispute?
Someone may have dropped the proverbial ball with regard to her violent proclivities, but it's far too late now for any second guessing.
Oh, and the gun in neither case, the professor or the partygoer, did one damned thing: People did something _using_ a gun, a gun neither you, I nor any other entity could have prevented them having if either was determined to have one.
Sorry, freedom is dangerous and expensive. Life is like that, guns or none.