I think it depends entirely on how IGA's team programmed it. More than likely, they would have set the "mourning" flag for whichever had the lowest register (the man, I think) and the other half would check the flag before detecting damage. At least in CV3, collision detection was handled at the start of each step. If Konami didn't check the mourning flag until the specific behavioral code (as opposed to the universal behavioral code like collision detecting), then theoretically you might be able to kill both at the same time. If they checked the mourning flag at the start of the step, though, then no.