Biographical sketches of loyalists of the American Revolution ..., Volume 2, by Lorenzo Sabine, has a compilation of several mini-biographies, including that of Henry Mansin.
Mansin, Henry. Native of Prussia. Emigrated to Philadelphia from London about 1772. Went to Jamaica and thence to North Carolina. After the rising of the people at Ninety-Six, South Carolina, he joined John Stuart, Superintendent of Indian Affairs, and retired to St Augustine, Florida, when he was appointed Captain in the corps of Rangers. He sold his commission acted as Stuart's* agent for awhile; and in 1777, went to New York and was commissioned Lieutenant in the Queen's Rangers by Sir William Howe. He went with the Royal Army to Philadelphia and was taken prisoner. *[Note: I'm also researching Alexander Cameron who was an associate of Stuart]
According to this site, Lieutenant Henry Mansin, a German speaking officer in the Queen's Rangers, entered Lancaster County, searching for recruits, horses and general support for the loyalist cause. On his second trip, in February 1778, several farmers caught Mansin and several of his co-conspirators stealing horses.
Henry Mansin and a man named Wendel Myer were hanged.
The General Orders for the hanging were found in "General orders...and Lt. Col. Wm. S. Smith":