Update:

Thanks to Peace giving me Sonny Ochs' email address, I posed the question to her, and she told me that, while it's one of her personal favorites, she doesn't know any more about the incident than what's in the song. Her theory is that he'd heard about it on the radio or read a news article on it.

With my fairly limited research skills, I doubt I could find anything further myself, although it would be interesting to see an original news article on it. There's always the library, but I doubt their archives of New York papers go back that far, and besides that, I don't know the year, much less the exact date.

Question for you guys: Is there any feasible way I could go about this, besides actually heading to New York and searching through the papers from the early 60s? I'm not much of an investigator, though.

Assuming Ochs didn't take too much license in the song, it looks like Marsh was a pastor, or maybe a priest in a church, which he left to work in the ghetto, but I guess there's no way to tell whether the church was near Spanish Harlem, or if he'd moved further to do his work.

How do people go about finding this kind of information? Has anyone here undertaken such a task?