Long Island man wearing 9kg-metal necklace dies after being sucked into MRI machine
(www.independent.co.uk)
The kill switch is VERY expensive to press, many thousands of dollars, and even when it does an "instant" magnet quench, by the time you hear the screams it's all over anyway, the metal has landed on the magnet. Quenching the magnet will make it let go, but it won't unbreak the neck bones.