His crew may have spotted him, but didn't pay him any mind until he spoke up. Observers were normal, as were those who were confused as hell about why these guys were lugging around barrels of weapons.

"Flashstones?" MarKus stops directing the loading and checking of stock to find out what the heck the guy was talking about, though, at least through logical clues tell him it's proooobably some manner of magical explosive rock.

Or a primitive grenade.