Active shooter situation there will probably be no time to call the police. At least not while you're still in harms way.
If you and yours can likely get to saftey without becoming a target then do so... if not draw and fire to at the very least supress the gunman while you make your exit.
Every store in a mall has a door to the outside. run into the nearest storefront and out the back. The gunman will most likely be in a common area of the mall.
"...with liberty and justice for all." (Must be 21. Void where prohibited. Some restrictions may apply. Not available in all states.)