I beleive, thoguht not sure, that there is a State Police barracks nearby..the local cops wouldn't have the available manpower, on a Sunday afternoon, that dast to lock it down, AND cordon off the surrounding area..
Yes, there is an SP barracks nearby.
It would take a lot of cops to cover all the exits and search the mall.
Notice how the story went from terrorists armed with machine guns to two gunmen armed with handguns?