Lewis Childs was surfing by himself off Neskowin in Tillamook County on Friday morning when something unusual happened: a 6-foot-tall dorsal fin broke the surface of the water about 30 yards from his board. A killer whale. “I knew it was not a dolphin,” the Portland musician said. “I wasn’t sure if it was a shark. I didn’t know exactly what it was. I just knew it was a big fin.” Childs had been surfing off Ghost Forest in Neskowin State Beach Pa…