In 2372 he was on duty on Ops when the Klingon boarding party beamed on board the station and tried to shoot at a Klingon. He was hit by a disruptor shot from one of the boarding Klingons. (DS9: "The Way of the Warrior")
Bertram was a weapons collector and in 2375 he tried to gain unauthorized access to the replication pattern for the TR-116 rifle which had been used to commit two murders on the station. His collection included Klingon, Cardassian and Federation weapons.
Ezri Dax, who was under the influence of Joran Belar, nearly killed him because she believed he might be the murderer. Bertram was ruled out as being the murderer, as he was on Bajor when Chu'lak murdered Hector Ilario, his first victim. (DS9: "Field of Fire")