In the spring of 1943 he was in charge of a Gestapo base in Nazi occupied France. Charged with stamping out the Free French resistance movement he captured two French freedom fighters named Lamonte and Farrotte. Hoping to get information out of them about the resistance before executing them Captain Brool was denied this privilege when the two men apparently died in their cells under mysterious circumstances.
In reality, the superhero known as Destroyer had smuggled in a drug that simulated death for a few hours in order to smuggle the men out of captivity. Brool stumbled upon this plot, but was beaten into submission by the Destroyer and handed over to the Free French resistance to be questioned.
It is assumed Brool was either killed by the resistance or was executed in the trials that would follow - he may of also committed suicide, as many other Nazis did upon capture.