There is a deep open gash on the boy's left leg. It's not bleeding(because he's dead) but looks like it has been wiped.(a smear appears lending from the wound upwards) It appears at 23-25 seconds into the video. Freeze Frame it and decide for yourself.
I know Hollywood can make some convincing special effects but not these clowns...
Saw it—thanks.
P.S. Good eagle eyes.