I think you will live longer if you do all that you can to avoid an active shooter.
He will have the advantage of choosing the time and weapons and all you will be doing is reacting with what you have.
Which, if you are at the typical workplace, will be spit wads.
Your best chances are getting 1) getting out of there, 2) if stuck, find a room and locking the door, calling the Cops, and hoping the gunman will find the next open room more inviting than yours. These nut cases are against a time limit once the authories are notified.
And don't trust people in uniforms. The Nut in Norway dressed as a Cop and told people he was a responder. When they got close he shot them. He killed 78 people or so.
If I'm not shooting, I'm reloading.