It was a British naval vessel under the command of a Captain Clarke, and had been sent to reinforce the garrison situated at Forthill, overlooking the town.
The garrison and its commander, Captain Anthony Willoughby, had been harassing the locals and bombarding the town on a regular basis for several weeks, and negotiations had been held between Willoughby and Walter Lynch, with the Earl of Clanricarde acting as mediator.
Shortly before nine a.m., Kirwin led a group of men including Brian Roe Mahon Móre, Walter Óge Martyn and other natives of the town.
They then sailed the ship into the quays while under fire from the Forthill garrison; they suffered no direct hits and promptly distributed the goods and military supplies that the ship had held for the garrison.
Kirwin may have survived the subsequent warfare, for following the surrender of Galway in April 1653, he and the rest of his followers were the only townspeople explicitly excluded from the Terms of Surrender.