I know a bit about these things, the brake (at the motor) fails to the on position and is released under electrical power that pulls against the closing springs. It is easily released though, manually, up close then you can hand wind it. Its counterbalanced like a lift, so not as bad as you think ( though if lightly loaded it will go up, not down!)
I think rather than a power failure, the overspeed governor has tripped and pulled in the safety gear.... that's not so easy, crane, winches etc.
It would have been safer to wait for a crane and man basket during the day, but in today's OMG freak out society, some poor sod had to dangle out a helicopter.