91 chevy electrical problems

hi guys, my truck was running today and just shut off out of nowhere. i turned the key to start it but it sounded like the battery was dieing because it would crank real slow and all. i held the key for a few secs and smoke came up from the back of the motor, does this sound like a starter or altenator or something?

sounds to me like a wire came loose or is corroded and not making a good connection at the starter.
this would explain the stalling all of a sudden too.
check and clean all of the connections at the starter and battery for starters.