It was BOTH hands. Just a regular two-hand roll. Since it was recorded independently from the WFD (world's fastest drummer) competitions, it's unofficial, but it's very close to the official records, give or take a few beats. His record was the fastest for a while, but it's been broken a few times now (Afanador, Verdi, Mangini...).
As for other "unofficial" drum speed records, I'm pretty sure Morbid Angel's Pete Sandoval plays the fastest double bass single strokes ever recorded on "Opening of the Gates". About 18/19 notes per second, more or less constantly throughout the entire chorus. That's about the same as the Berzerker, but with the feet.