Even if the zone itself is “safer” for criminals, they gave to leave the zone sometime, and thus expose themselves to severe retaliation.
Which may or may not come in the form which they delivered it.
Has there ever been a successful escape from a “gun-free” shooting site, in which the perpetrator could walk about afterward? Many times, the perp takes his own life. Sometimes, the pursuit make take several days, or even longer, but eventually, somebody, somewhere, pieces it all together, and the timeline is established.
In coward county Florida, the shooter walked out of the area among the students who were escaping.