Carlson was an angry, mentally unbalanced person. Prior to 2260, he lived on the Vega Colony, where after a series of misfortunes (including losing a job, his apartment, and having his wife walk out on him) he suffered a psychotic breakdown. After setting off a series of bombs on the colony, he relocated to Babylon 5 where he was hired by the station maintenance division. After only a few weeks, he began detonating several explosive devises around the station. The targets were random, though often included heavy casualties. After each explosion, Carlson would linger around the wreckage, absorbed in the death and chaos he had caused. This is how station security was able to link him to the bombing.
Carlson, cornered in his quarters, demanded Captain John Sheridan enter alone to negotiate. Carlson hoped to escape the station, but as a contingency had planted a large bomb in the station's fusion reactor. Sheridan attempted to talk with him, but once Carlson realized the captain had an open link, he tried to detonate his bomb. Although Sheridan was unable to prevent his using the detonator, station security had been able to find his bomb and remove it. Carlson was subsequently taken into custody.