I thought they (the attackers) were exchanging messages but realizing he was alone, I think the scream was actually a battle cry.
Utoeya Island massacre survivor Ingvild Leren Stensrud • Describing what she saw and heard, the day Anders Behring Breivik attacked Oslo and Utoeya, while testifying in the Norwegian killer’s trial. Stenstrud survived the attack, with a gun shot to the left thigh, after being knocked over — and subsequently covered by — the body of another victim. Glenn Martin Waldenstroem, who survived being shot in the face, asked that Breivik be removed from the room before he testified. With Anders gone, Waldenstroem told the court that the killer “looked angry and smiled simultaneously.” source(via • follow)