Posted on findagrave.com:

John Harris Kinzie Jr. was the son of John H. Kinzie and his wife Juliette Magill Kinzie, born October 21st, 1838 and died on June 18th, 1862. John Jr. was married to Elvenah Janes Kinzie, and a daughter was born to them shortly after his death. John H. Kinzie Jr. was killed on the USS Mound while they were attacking a fort on the White River in Arkansas. A shot from the Fort's batery penetrated the ship's boiler and an explosion occured aftwards, scalding most of the men onboard. As they were blown off the gunboat, a sniper began shooting the men as they tried to get back on the ship. John H. Kinzie Jr. was attempting to get back on the ship when he said to a another Navy comrade, "We have taken the fort, I am ready to die now" He died the following day of June 18th 1862.

From the Boston Herald, US. 23 June, 1862
Second Master Heath, 3rd Master Kinzie, 4th Master Seaville, Master's Mate H. P. Browne, Paymaster Chief Engineer John Cox, and assistant Engineers John McAfee and
Hollingsworth were killed. Pilot Chas Young was severely scalded and reported since dead. Surgeons Jones and Carpenter, Manning were slightly scalded. From eighteen to one hundred of our Sailors have already been buried and over twenty are missing.

Memphis Daily, April CS.
The War in Arkansas, full details of the explosion on the Mound City.
The Mound City crew numbered 175 officers, and men. Sad to relate, only from twenty to twenty-five, including the three officers above hand, escaped uninjured leaving one hundred fifty men killed, drowned missing and wounded! The mortalities are fearful. At the present writing, Thursday, June, 10 AM. On gunboat Conestoga, in sight, of Memphis, one hundred have died, while the recovery of the remaining fifty is considered doubtful.
We left forty three dead bodies on the Mound City, awaiting internment at Fort St. Charles. Since leaving there, thirty four have died on the Conestoga and Musselman, while Master Downing and all who witness poor man struggling and crying out in the water for help, are positive that from thirty to forty were drowned before assistance could possibly be rendered them, as before stated. A number were cruelly shot in the water by the enemy's sharp shooters from both shores and from the other boats. In the excitement and confusion attending the sudden and unexpected accident, the muster and description rolls were left on the Mound City. Therefor we have not been to give the names of one tenth of the forty three dead left on the gunboat. James A. Duffy, First Master of the Conestoga, was left in charge of the Mound City. She can be repaired wheee she lies without delay but, as really all her men were killed and wounded, a new crew must be furnished from receiving ship Maria Denny, lying off Cairo.