So after a bomb threat
People are walking calmly through the campus (mainly he and his students walking through a parking lot) to their vehicles. Wouldn't they be made to wait until all areas were checked and cleared?
Also, if you listen to Kim's story, it seems she married Guy and then divorced him when he became abusive. Now she carries a gun for protection against him. When exactly did she find the time to confide in him that she had a crush on her professor? I got the sense the the marriage was ended before she started school. But even if that weren't the case, how much would she have said to her husband or her abusive, ex-con, ex-husband that would make him think that he now needs to protect her from Jack?