During the critical moment, Zhang Heng turned to his side, barely avoiding contact with the rock. He did not see the black shadow behind him, nor did he hear the other person's footsteps. He did, however, notice someone coming from behind. Speaking of which, the sandstorm turned to be a blessing in disguise.
To avoid inhaling in too much dust, Zhang Heng kept his back faced into the wind, It meant the wind blew directly at the assailant as well. The assailant's body would block a part of the wind and sand as he approached, allowing Zhang Heng to sense the changes in the wind. This was how he dodged the lethal attack from his enemy.
On the other hand, the attacker was too slow to react, not expecting Zhang Heng to survive the surprise attack. While he was still stunned, Zhang Heng elbowed him, and he fell to the ground with a thud. Although his face was covered, Zhang Heng easily recognized the attacker as Bruno judging by his size.