#2 and #3 the deputies are trained to handle these situations. Their response varies at times. Most of the time they go to a call or near the call and wait for more back up. ESP when there is violence involved in the call. The Supreme Court ruled that police and law enforcement are not obliged to save your live or help you at all. Their bonds and insurance dictate their response. So shareholders and executives enforce the law.
Students were ordered to stay in place after the shooting was confirmed after the fire alarm. Holding students in place at school is the standard everywhere. Imo this move was not done with safety or the best interest of the students and faculty. It was done to minimize damages and costs to insurance companies spreading the burden and liability.