Chuckling, Sal nodded. "If I was going to backstab you, I'd let you know first. Besides, you're useful to me. I'm useful to you. We're similarly disinterested in offing each other at the moment."
Standing up on the ledge, Sal rounded Light, but not in a creepy way. Rather, he watched him from behind. "Most of the birds are gone, but there are still a couple. Try to shoot one; I want to watch you from here."
Sal had no interest in kicking Light off the building, though it'd be funny. Rather, he wanted to observe and improve where Light needed to be helped.