A community member at Alki Beach reported to police a man in the area was armed with a large gun Saturday evening.
Around 8:00 p.m., after receiving this information, officers searched and located a man matching the description of the possible suspect.
The male suspect ran from officers but was detained shortly after with a firearm in his possession near the intersection of 58th Avenue Southwest and Alki Avenue Southwest.
The 15-year-old suspect was arrested for unlawful possession of a firearm and booked into the King County Child and Family Justice Center.
