Utah ? Faced with a backlash over dimming hopes, a coal mine boss broke his self-imposed silence Monday to issue e-mails lowering expectations that six trapped coal miners will ever be recovered, dead or alive.

Bob Murray, chief executive of Murray Energy Corp., issued an initial statement that promised “we will not be deterred, and we will not leave this mountain until we find our people.”

That was followed a few hours later by another release, saying: “We will not leave this mountain until we achieve a resolution to this tragedy.”

The once-outspoken Murray had been noticeably absent from meetings with relatives and from news briefings since three rescuers were killed last week in a tunnel collapse. Family members said they were upset by his absence.