'First' was the leader of a group of five Borg children who were stranded in space. Their cube had become disabled following the deaths of the adult Borg, and the children were disconnected from the Borg Collective.
'First' and his group had captured USS Voyager officers Tom Paris, Chakotay and Neelix, and were holding them hostage in exchange for Voyager's deflector dish. Seven of Nine tried to explain to 'First' that he and the Borg children were not going to be rescued by the Borg, since their distress signal was ignored. 'First' became so enraged that he tried to kill Seven, but was stopped by the other children.
'First' refused to evacuate the cube when its power induction grid became unstable. He was electrocuted and died when he attempted to fix it. His last words were the Borg mantra "We are Borg," to which Seven responded: "Yes, we are." (VOY: "Collective")