The attack, which came as the teenagers huddled under a tree in the rain, was intended in retaliation for a July attack against Mr Williams, who declined to prosecute a suspect in that shooting, Mr McCarthy said.

BBC: Kenneth Williams (left) and Michael Ward booking photos

In the predawn hours before the attack, he called his police handler, met him near the Temple Under a Big Tree, and told him about the murder plot and about Siu.

NEWYORKER: The God of Gamblers