A video interview conducted by the PlayStation Blog with Guerrilla Games’ Managing Director Hermen Hulst shows the Sharp Shooter attachment in great detail, along with some brand new gameplay footage from Killzone 3 (played with the PlayStation Move, of course).
In the video you can also spot the Move controls settings screen, which I’ll post here for your convenience (click to enlarge).
It also turns out the Sharp Shooter attachment was designed by Guerrilla Games in conjunction with Zipper Interactive, the developers of the Move-supporting MAG and SOCOM 4.
On a side note, I was informed by a Zipper representative that the special reload buttons located on the Sharp Shooter are not linked to any specific Move button. Those are brand new buttons that developers can map to whatever they want.