((I think Mercy was saying he's going to cast Thunderclap on the far side of OUR Room- on this side of the protective glass panelling. Thus not destroying the computers that we need to finish this run. Hopefully.))
I'll hold my gun inside my tools, and fake a fall from the venting duct I'm sitting in. Maybe they'll just think I fell victim to whatever took out the guard, maybe they'll check on me, or maybe they'll just wait long enough for Mercy to take them all out with a spell.
I don't know if any of those will happen, but I'm going to fake a fall, dropping some tools but hanging onto my belt, gun saftely inside. I'll fake some sort of seizure once I hit the ground, too, just for good measure.
Acting check. Defaults to Charisma. target number 4.