A Coast Guard helicopter went down in Mobile Bay, Ala., Tuesday night during a training mission, leaving one dead and three missing. Rescue crews found one crew member of the MH-65C helicopter unresponsive after the aircraft crashed three miles from shore. “Our thoughts and prayers are with the families of the crew members during this difficult time,” said the commanding officer of the Coast Guard Mobile unit. Rescuers worked all night to look for the three remaining crew members. A coordinated air and sea search was reportedly impaired by heavy fog in the area. The cause of the crash was not known as of Wednesday morning.