Carlson was an angry, mentally unbalanced person. Prior to 2260, he lived in 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. He was hired in January 2260 in station maintenance, division 11. After only a few weeks, he began detonating several explosive devises around the station. The targets were random, and often caused 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, with the help of Brother Theo's Trappist monks.
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.