Episode 407, "Shockwave"
SEASON 2, EPISODE 203 - Haunted by ghosts of those he previously killed, a SRU veteran turns up at headquarters and holes himself up in a safe room where he intends to commit suicide. He diverts the team with a false bomb threat with an ominous suitcase, and gets them to abandon the station. Ed gets wind of the suicide attempt. Having trained under this veteran for many years, Ed, eyes flooding with tears, is able to talk his former mentor down and out of the room.