When we talk about mass shootings we're likely talking about the U.S. where (For better or for worse) weapons are as common as grass and the ability to carry concealed is a legal right in a number of states.
Simon and LUHE are talking about a city where anything larger than the tiniest of pocket knives is illegal to carry in a public place. The logistics of law enforcement are understandably different when illegal weapons are that easily concealed.
Here in the U.S. law enforcement definitely does associate certain crimes with certain profiles. Immediately after the Oklahoma City Bombing, for example, authorities had a good idea what type of person they were looking for. --An angry white male.
Two innocent men who seemed to fit that profile were dragged out of their hotel room in Springfield MO and treated quite roughly.