My thoughts: his corpse was always planned to be found dead as he probably would not have done the planned shooting, they just need a fall guy and to destroy the lives of anyone with pesky eye witness testimony or worse recorded evidence of who really did it.

When the call came in (for whatever reason) to scrap the plan, mr. patsy was already dead and dressed for the part, so all that happened after was to write a note on the women’s room stall. It’s imperfect though as it should be just as easy to remove him and try again later rather than put everyone, civvy and WH alike, on high alert.