Once the elephants had crossed, or were crossing, the river, Metellus sent his light infantry to skirmish with the Carthaginians and impede their passage. These light troops hurled javelins at the Carthaginians, and had been instructed to concentrate on their elephants. Panormus was a major supply depot, and townspeople were employed in carrying bundles of javelins from stocks within the city to the foot of the walls so the Roman skirmishers were constantly resupplied. The ground between the river and the city was covered with earthworks, some constructed during the Roman siege and some part of the city's defensive works, which provided cover for the Romans and made it difficult for the elephants to advance, or even manoeuvre. The elephants' mahouts, eager to demonstrate their charges' prowess, nevertheless drove them forward. Some accounts also have missiles being hurled down from the city walls at them. Peppered with missiles and unable to retaliate, the elephants panicked and fled through the Carthaginian infantry behind them.