What was he doing in Pittsburg at 3 in the morning?

It's a question that police and everyone who knew 22-year-old Benjamin Merrill are asking, and so far there isn't a whiff of an answer. The San Francisco waiter and Seattle-area native was found shot to death early Tuesday at Marina Walk Park.

Merrill had no known ties to the city. But there he was found, with no wallet and no ID. He was labeled a "John Doe" for two days until he was identified through a fluke.

"All his friends are all shocked," said his father, Peter Merrill. "It makes no sense why he's over there. It's a big mystery: They don't think he'd gone over there before, and certainly not in the middle of the night."

His identity might still be a mystery if his father's cousin, Frank Merrill, wasn't sitting in a San Mateo courtroom Wednesday. Frank Merrill — attending the trial of the man charged with killing his stepson, East Palo Alto police Officer Richard May — was seated next to a detective and saw him looking at a police sketch.