Essentially, it's an explosive device that releases radiation, heat, and an explosion. Without going into too much detail, it's capable of devastating an entire city easily, while still being the size of a conventional bomb, and leaves effects for a very, very long time.
... Imagine the abysmal luck a human would have to be caught in a blast such as that. Now imagine the luck a human would have to be caught in the blast with their brother.
That was one of the worst endings to a life I've had... but it was not unusual in its cruelty, not in the least.
Is it any wonder why I'd do nearly anything to find peace?