Seattle Police say a 32-year-old man is under investigation for arson after a witness allegedly saw him leaving the scene of a fire at a construction site in South Seattle. This is the second time in less than a week that a fire has been set at the site. Police say the witness had gotten out of bed around 3 a.m. Friday when he saw a flickering light outside the window of his home in the 2300 block of South Plum Street. The man realized a nearby construction site was on fire. He told police he saw a man leaving the construction site, so he got on a bike and followed him. The witness confronted the man and pinned him down to the ground and held him until police arrived.