(Portland, OR)  --  A Portland teenager is recovering from a severe concussion after a spontaneous snowball fight with strangers turned violent.  Police say 16-year-old Julian Calderon was walking near Northwest 23rd Avenue with a friend Tuesday when a family picked a snowball fight with them.  Calderon tells KATU the innocent fun turned scary when a man from the family picked him up and threw him on his head, knocking him out and causing him to suffer a seizure.  The family allegedly fled the scene.