Well, the actors might be returning after their post-performance festivities, but I see your point.
It's my understanding that suppressors do not cancel the sound. They reduce it. I watched a video on youtube about this, where a guy fired weapons with and without suppressors. Maybe it was a bad video, but the point (which seemed supported) was that suppressors reduce sound but they aren't like in the movies where nobody can hear anything. Maybe you can't hear it from 100 feet away but 10 feet, sure.
I never spent much time on the streets of New York at 6:45 AM, but it wouldn't surprise me if there was enough extraneous noise to at least partly mask the shots. That could have happened.
But it's still fucking brazen to shoot a guy on the city street when cars and pedestrians can have full view.