"This is for you, Frank"

I was just leafing thru the Valachi Papers for the millionth time and came across the attempted assassination of Costello. I'm trying to figure out a reason for the Chin to call out to Costello before firing at him. I can't come up with any. When I first read the Valachi Papers eons ago I figured the Chin was just a dumbfuck street soldier, but the years have proven he must have had a little something going for him, despite his feigned craziness. Any theories?

A stupid, dumb mistake by Gigante. Probably nothing more than that.

Maybe Gigante was trying to catch Costello's attention, make him stop walking and thereby turn a moving target into a stationary one..

He was told to say, "Michael Corleone says hello," but he forgot.

I didn't know The Godfather came out in 1957!