Source: http://www.nypost.com/p/news/regional/brooklyn/so_much_for_packing_um_rod_jXKO6I6jK3RgVNDNWClDoI
Typically, in an effort to avoid arrest, such bone head mistakes are attributed to a jealous girlfriend who discovers that the victim has another, or a jealous boyfriend who's squeeze the victim was attempting to hit on. However, the downward linear path of the projectile is usually a dead giveaway that the injury was accidentally self induced. That is, if someone else did it to them, then it's usually a direct path into the groin instead (which is a lot worse). Either way, it's good that another young thug (and a gun) is off the streets.