Weren't they planning on herding everyone to the roof and blowing it up?
The plan was to do that to cover their getaway. Herd the hostages up to the roof, nominally to stop snipers while they got in a helicopter. Then flow it all up. By the time they sorted the body parts and realized they weren't there, they would be gone and safe by a different route.
This is also why getting the detonators back was so important. Without them, they couldn't blow the roof.
Me too, because after I posted that, I also remembered his monologue about how if you steal $100M in bearer bonds they will find you unless they think you are dead.
So yeah, I don't remember if it was discussed but I think McClane just sped up the timetable for getting the authorities involved. They definitely tried to keep it quiet at first though.
But also, Mr Takagi was murdered before John had done anything, IIRC.
