If you click on the icons they give you more detail as the the nature of each crime. Most of the ski-masks seem to be "STRONGARM ROB." which implies a mugging

If you click on the icons they give you more detail as the the nature of each crime. Most of the ski-masks seem to be "STRONGARM ROB." which implies a mugging to my mind. The gun symbol means weapon, and most of them seem to be knives.