how many grenades does 1 person normally carry - 2 have been used against us so far, with our special harness we can manage 3, but an average grunt doesn't have such equipment. So our choices are a: the guy is out of grenades b: we are facing someone with significantly better than average equipment, or c: there's more than 1 person.
I would rule out b, because slightly more exotic grenades would have been used against us in a supprise first strike.
Also, the "efficient killing" reported earlier doesn't mesh with indiscrimanant grenade tossing we are facing atm.
finally, the guardsmen who are escorting the supply person should be here soon. Lets hope that they aren't the ones tossing the grenades.
Blind-fire is all good, but aim at the door-way... and why are we being cautious? after the blind-fire either the chaos corrupted will continue charging and peaking out will not help other than give up the initative, or the other guy will take cover and not expect use to Daringly vault over the table (on the off chance there's a third nade, we'll have no cover anyway, so we might as well take the initiative) Therefore: lay down covering fire for ouselves, then vault the table, reading the shotgun and Clense the Room of whoever comes through the door next but don't bust out into the hall until we know a bit more -- aim to end up standing next to the door covering it with the shotgun.
For The Emporer!
i'm not sure about the 'nade - throwing one when we haven't even seen the opposition ....)
(note: i don't know much about the 40k universe ...)