Quintus Curtius Rufus, History of Alexander 9.4.32

9.4.32

nam ipse eminus ex turribus petebatur, nec subire milites poterant, quia superne vi telorum obruebantur. Tandem magnitudinem periculi pudor vicit: quippe cernebant cunctatione sua dedi hostibus regem.

The parapet which ran round the rampart was narrow, and was not marked out along the coping with battlements and embrasures, but was built in an unbroken line of breastwork, which obstructed assailants in attempting to get over. The king then was clinging to the edge of the parapet, rather than standing upon it, warding off with his shield the darts that fell upon him from every side, for he was assailed by missiles from all the surrounding towers. Nor were the soldiers able to mount the wall under the storm of arrows discharged against them from above. Still at last a sense of shame overcame their fear of the greatness of the danger, for they saw that by their hesitation the king would fall into the hands of his enemies. But their help was delayed by their hurry, for while every one strove to get soonest to the top of the wall, they were precipitated from the ladders which they overloaded till they broke, thus balking the king of his only hope. He was in consequence left standing in sight of his numerous army, like a man in a solitude, whom all the world has forsaken.