Joshua 8:19-20

8:19 When he held out his hand, the men waiting in ambush rose up quickly from their place and attacked. They entered the city, captured it, and immediately set it on fire. 8:20 When the men of Ai turned around, they saw the smoke from the city ascending into the sky and were so shocked they were unable to flee in any direction. In the meantime the men who were retreating to the desert turned against their pursuers.