Jack Barr was a victim, being a slave to the WTS, but he was also a slave master. In this case he is both the perpetrator and the victim.
Although every human death is a loss, his death could have positive consequences. Maybe the GB will become more hardcore and more people will leave because of it. In that sense, Jack Barr's death could be something to be happy about, even though it is a personal tragedy.
Of course we would all rather have Jack come to his senses before dying, waking up from the heavy WTS yoke and actively try to free as many faithful sheep as possible.