When the Constellation encountered an extragalactic "planet killer," Masada was beamed down to L-374 III with the rest of the Constellation's complement by Commodore Matt Decker, and was killed when the device destroyed that planet. (TOS: "The Doomsday Machine")
Background information Edit
This character was only mentioned in dialogue.
According to the Star Trek Encyclopedia (4th ed., vol. 2, p. 25), Masada was probably "named for the hilltop fortress where Jews defied Roman legions, eventually committing suicide en masse rather than surrender."