Lorgal was an anti-Republic radical bent on destroying the Galactic Republic through terrorist actions. Styling himself "Lorgal the Great Liberator", he was responsible for over two dozen bombings and hundreds of civilian deaths.
During the height of the Jedi Civil War, Lorgal was arrested and imprisoned in the Republic Embassy on Manaan, from where he was to be transported to Coruscant and given a fair trial. It was no secret that many of the Republic soldiers guarding Lorgal wished him dead, so the criminal was placed in an isolated force cage chamber that both contained him and protected him from any potential harm from the outside. In a way, Lorgal was pleased with this turn of events: he could taunt Republic personnel who passed by his cell without fear of reprisal, and, when his trial eventually arrived, the coverage of it would give him an opportunity to voice his revolutionary message to the galaxy as a whole.
He was most likely eliminated by a GenoHaradan agent before his trial on Coruscant. The GenoHaradan had a vested interest in the Galactic Republic, ensuring its survival for 25,000 years by doing its dirty work in secret. As a potential threat to the Republic's stability, Lorgal soon became a target for the guild.
In an optional dark side quest of Star Wars: Knights of the Old Republic, Revan took the GenoHaradan assignment to have Lorgal killed in his holding cell on Manaan. Revan first met Lorgal with the latter in his protective force cage and it strengthened his resolve to carry out his mission. Revan accomplished this by secretly slicing the computer terminal near Lorgal's cell (or perhaps having his droid T3-M4 slice it) and reprogramming the cage to execute its prisoner. Spiteful of the Rodian terrorist, the Republic guards looked the other way as Lorgal screamed his death throes.
Alternatively, Revan could have killed Lorgal with Force choke or Force lightning, if the player had developed these powers.