At 3:43 you can see that his left foot is on the line. When he, as a back row player, jumps off in the front zone, he's not allowed to hit the ball while it's fully above the net (source: rule 13.2 FIVB, www.fivb.org/EN/Refereeing-Rules/documents/FIVB-Volleyball_Rules_2017-2020-EN-v06.pdf)
