If this had occurred at the time of the nations founding, the killers would have already seen justice at the end of a rope. It would not have been considered “cruel and unusual punishment”. In addition, their right to a speedy trial by a jury of their peers would have been delivered. The appeals process, if permitted by the court, would have been expedited, consistent to the right to a speedy trail.
How far we have fallen since then.
Being kind to the cruel is being cruel to the kind.
The left thinks the modern world is more moral than the past. Perhaps in some ways it is, but in many ways it is not. (As this example shows).