The advice which is issued by the Counter Terrorism Policing, is in the rare event of a firearms or weapons attack to:
RUN to a place of safety. This is a far better option than to surrender or negotiate. If there's nowhere to go, then...
HIDE. It's better to hide than confront. Remember to turn your phone to silent and turn off vibrate. Barricade yourself in if you can. Then finally, and only when it is safe to do so...
TELL the police by calling 999.
The video below also explains this, and there are posters available which you can download and display on noticeboards.
