Kind of a contradiction since Arisato DOES NOT USE PISTOLS.

He can use any weapon he wants.

Steak said:
He can use any weapon he wants.

Gun's my man, only Aegis uses gun's.

Evokers, mon cher. Evokers.

Here's a possible explanation. It's Naoto. Wearing the wrong uniform. And... using a pistol instead of a revolver.

...yeah I'd say it's safe to assume that it's Arisato with an evoker.