He died in June 1863 on board his ship USS Albatross while taking part in the Union attempt to blockade the Mississippi River.
His grandfather John Elliot Copp, for whom he was named, and his uncle Ezekiel Bishop Hart were both killed serving in the Navy during the War of 1812.
In late 1846 he was admitted to the newly opened United States Naval Academy and graduated as a Passed Midshipman in the class of 1847.
Following the outbreak of the Civil War he served aboard USS Vincennes, and was part of the West Gulf Blockading Squadron on the Mississippi River under Admiral David Farragut.
They were put in contact with Confederate Army Captain William Walter Leake, a company commander with the 1st Louisiana Cavalry, who was home on furlough.
A truce was arranged so that the Union officers could bring his body ashore, attend the funeral, and return to their ship to resume their blockade.
Leake was buried near Hart, and the two former enemies are commemorated with a single marble slab, placed in 1955 by the Grand Lodge of the State of Louisiana and "dedicated to the universality of Freemasonry.
In 1999 he and the St. Francisville lodge cooperated in staging a reenactment of the truce and burial, billed as "The Day the War Stopped;" the tradition has been continued annually in June ever since.
During the 2000s Karwowski began to contact descendants of Hart and Leake, inviting them to attend the re-enactment weekend, and several have done so, particularly in 2013 for the 150th anniversary of the event.