On that video, YouTube user septichar commented:
Chris Penn said: ’‘What was supposed to happen—and I don’t know if Quentin’s gonna like me for giving this away, but it’s too late now, he never told me not to—was Harvey Keitel was supposed to shoot Lawrence Tierney, then me, then get squibbed. But what happened was the squib on Harvey went right off after he shot Lawrence Tierney, so he went down, but my squib went off, so I went down. Quentin said, ‘You know what? It’ll be the biggest controversy of the film. We’re leaving it.’”
I’m guessing he’s quoting from some interview. Makes sense to me.