The gunboat had been preparing to head to sea to assist a disabled warship (the monitor Wyoming) when her boilers exploded, killing 66 sailors and injuring over 100 more. The ship was so badly damaged that she had to be grounded to keep her from sinking and she was soon retired and sold for scrap.
In 1908 a monument was erected in memory of those lost in the disaster.
Thanks, Stonewall, for adding more information about the base at Coronado.