Having landed in civilian clothes, the authorities accused him of being an impostor and ordered him to show his commission.

The Lieutenant produced it, whereupon they declared it a forgery and arrested him on the charge of being a pirate.

After he and a midshipman who accompanied him had been insulted repeatedly they were allowed to leave.
When Captain Porter learned of this outrage he entered the harbor with several of his vessels and sent a letter to the alcalde or governor, notifying him that he had one hour in which to send an explanation of his action.

While waiting for the return of the flag of truce Captain Porter saw one of the shore batteries getting ready to fire upon him.
Instantly, he sent a detachment, which captured the battery and spiked the guns.

Then Captain Porter landed, and, after spiking another battery, made his way to the town.