UPDATE 2/14/2017: CAPTURED! High Fives all around to the Waukegan Police; they spotted the McStabber RETURNING to the scene of the crime on Tuesday morning, wearing the same jacket and mask. The dude said he just felt like stabbing someone.
Dunno if it is just from distortion, but it kinda maybe looks a little like Mr. or Ms. White Legs McStabber may be sporting some leg tattoos. McStabber looks like he or she may be right-handed and may have rehearsed some Hollywood cinema knife moves; the 50-year-old McStabbing victim suffered multiple wounds but none were reported to be existentially significant. Police reported that it initially appears McStabber and McStabbee did not know each other ... so we may have some weirdo doing this randomly, just for the hell of it; could be on a dare from peers; could be a social club initiation, could be he / she is just violently mental; for now, we don't know. McStabber was not very good on this attempt ... I would not want to bet on this schmuck remaining incompetent with a knife.
McStabber's mask looks like it may be something called an altitude (or elevation) training mask; I fished an image (below) from the 'net.
Call the Waukegan Police if you have anything that may help.
All McStabbers are innocent until proven guilty by a court of law.