Apparently an off-duty officer in Western NY State went to an outpatient imaging center. Here is the case report. The officer was carrying his Colt 1991-A1 compact. Due to a miscommunication with the technician and the officer, the officer entered the MRI room with his firearm. He attempted to set the firearm down on top of a cabinet that was 3 feet away from the MRI magnet bore. The magnet pulled the gun into itself. When the gun struck the side of the magnet it discharged a round. No one was hurt.

They shut down the magnet to remove the gun. According to reports, the gun was still in the cocked and locked position. There was an empty cartridge in the chamber.

This is how Bearing Arms explains what happened:

When the firearm was removed from the magnet, the gun was still in a cocked and locked position. An empty cartridge was found in the chamber. The presence of an empty cartridge in the chamber is highly unusual. If the thumb safety were not engaged and the weapon fired normally by depressing the trigger, the normal backward recoil of the slide should have automatically ejected the empty cartridge, and a new live round should have automatically been chambered. As discussed earlier, the thumb safety performs two functions: it prevents the sear from releasing the hammer, thereby preventing the hammer from striking the firing pin; it also locks the slide in place, preventing retrograde motion of the slide and automatic ejection of the empty cartridge. Thus, the presence of an empty cartridge in the chamber confirms that the thumb safety was engaged at the time the gun was fired. Given that the thumb safety was engaged when the gun discharged, it is also likely that the normal trigger and hammer mechanism of firing the gun was bypassed because the thumb safety would have also prevented release of the hammer.

The gun likely discharged as a result of the effect of the magnetic field on the firing pin block. The firing pin block was probably drawn into its uppermost position by force of the magnetic field. The firing pin block has to overcome only light pressure from a relatively small spring to release the firing pin. The pistol was likely drawn into the magnetic field so that the muzzle struck the magnet’s bore first. With the firing pin allowed to move freely in its channel, the force of the impact on the muzzle end was sufficient to cause the firing pin to overcome its spring pressure and move forward to strike the primer of the chambered round.

This account explains how the weapon discharged when the thumb safety was engaged.

Sounds like a very rare occurrence. Or perhaps machines are rising up to take over the world.