Cruel and unusual punishment is about sentencing, after a trial. These folks didn't go through a trial.
No, I don't think either person deserved fifteen years of hard labor, or five years.
What actually happened is not that they were executed on the spot, no.
Oh, just spontaneously died then? You know if you play the video backwards it shows ICE applying lifesaving bullet removal techniques on Mr. Pretti and Mrs. Good
It's not a particularly strong argument that these agents didn't violate the 8th amendment because they violated the 6th amendment right to trial.