Quintus Curtius Rufus, History of Alexander 8.14.31

8.14.31

cum Porus destitutus a pluribus tela multa ante praeparata in circumfusos ex elephanto suo coepit ingerere. Multisque eminus vulneratis expositus ipse ad ictus undique petebatur.

Hence the elephants, being at last spent with wounds, spread havoc among their own ranks, and threw their drivers to the ground, who were then trampled to death by their own beasts. They were therefore driven from the field of battle like a flock of sheep, as they were maddened with terror rather than vicious. Porus, meanwhile, being left in the lurch by the majority of his men, began to hurl from his elephant the darts with which he had beforehand provided himself, and while many were wounded from afar by his shot he was himself exposed as a butt for blows from every quarter. He had already received nine wounds before and behind, and became so faint from the great loss of blood that the darts were dropped rather than flung from his feeble hands. But his elephant, waxing furious though not yet wounded, kept charging the ranks of the enemy until the driver, perceiving the king's condition — his limbs failing him, his weapons dropping from his grasp, and his consciousness almost gone — turned the beast round and fled.