Possibly to close off radio detonation, not all systems work as well as the movies. Maybe to contain blast damage if it were to go off. They do a lot less damage to other properties and people when things go pop inside four walls.

If you wish to disarm a device, it's not like a Hollywood film, cutting a red wire or a blue wire. It could be tripped, tilt sensored or even a booby trap placed on top of the main device.

He took the right course of action. Away from the public arena (blast damage can blow windows out several streets away). Contain the risk. Then find a nice quiet area to study it and see what makes it tick.