(Portland, OR)  --  Portland Police are trying to identify the people responsible for Saturday morning's mass shooting downtown that left one woman dead and six people injured.  The Portland Police Bureau says no arrests have been made in connection to the shooting, which happened around 2 a.m. near a collection of popular food carts at Southwest Oak and 3rd Avenue.  Investigators say it's too soon to say whether the shooting was gang-related.  Police believe several potential witnesses ran from the scene before speaking with detectives, and they're urging those witnesses to contact them.