Almost completely unprepared for this one... (Haliaeetus leucocephalus)

I was doing my best to drive myself irreparably insane trying to get one really good shot of a barn swallow now that they're back when this eagle surprised me. I saw a largish bird coming my way from across the park and figured they were probably a gull, and then I noticed an eagle farther away, being harassed by a crow, and THEN I realized the bird flying toward me was in fact an eagle and I barely had time to aim at them and focus hastily and get this one (relatively) good shot. I think they were at most fifty feet (15.2 meters) off the ground when they flew directly above me.