I wanted to add something to this conversation I had neglected to mention before, which in my mind points to Gambino as the likeliest suspect or at least the one with a lot of motivation to do so. I'm surprised I haven't seen mention of it in 114 preceding posts in this thread, but I think it's well worth bringing up in establishing further intent on Gambino's part.

According to a 1971 report in the New York Times, during a heated argument over the League, Colombo allegedly spat in Carlo Gambino's face.

Now I don't know about you, but with rare exception I would think it is not an unrealistic assumption to make that no matter who you are - if you spit in Carlo Gambino's face...well I'd say you'd likely have more time on this earth with a Pancreatic cancer diagnosis. I can't possibly imagine any scenario in which Gambino allows that to go unchecked.

I'm sure Colombo had plenty of other enemies and so it doesn't discount other theories by itself, but it certainly adds more motive to Gambino. Add that to the shooter being tied to known Gambino and Lucchese hangouts and associates and the picture begins to get a little clearer.

I really do think the likeliest signs with what evidence we have to work with point to Gambino, looking to hang blame on Gallo. Particularly with the use of a black man; many old timers didn't like Gallo's associations with black gangsters so it serves as a fitting bit of symbolism there.

Gambino was a shrewd guy, easily one of the best bosses of all time. This was an opportunity to get an annoyance out of the way as well as exact revenge. I would be more surprised at Gambino's character if he did not take advantage of this opportunity than if he did.