The novel states that Sonny lived on the mall. But after Vito is shot, Clemenza knocks at the door of Sonny's kitchen, and it appears like an apartment somewhere in the city. If it was at the mall, why would Sonny draw a gun?
So, does the film change it for the sake of drama? Or do we have to assume that Sonny was so scared that he feared assassins on the mall?

BTW: Is it "at the mall" or "on the mall"?

Well, of course Sonny was scared. Someone had just tried to murder his father.

What's a mall? Like as in stores?

Was Clemenza in on it? The mall was relatively unprotected at the time.

Either in or on the mall is appropriate.

Sonny lived on the mall. In a deleted scene, you see him walking in an inside passageway in the mall to his mother's kitchen.

So he prpbably had a residence there with a small kitchen for his family's private use. With all the money the Corleones had you'd think he could have afforded a notepad by the phone so he wouldn't have to write on the cabinet.

In this case "the mall" is a collection of residences on a private street... like a compound.

DT, I'm confused by your's and TB's references to an inside passageway. What and where?

Watch at 5:29

I don't understand this. After the call from Sollozzo, he leaves his house and walks across the mall to his father's house and eventually enters his father's office. What's the "inside passageway in the mall to his mother's kitchen"? What's the "small kitchen for his family's private use"?