Answer by taking a quote from the following article:

Osceola was named Billy Powell at birth in 1804 in the Creek village of Talisi. now known as Tallassee, Alabama, in current Elmore County. "The people in the town of Tallassee...were mixed-blood Native American/English/Irish/Scottish, and some were black. Billy was all of these."

After Osceola's death, army doctor Frederick Weedon persuaded the Seminole to allow him to make a death mask of Osceola, this being a European-American custom at the time for prominent people. Later he removed Osceola's head and embalmed it. For some time, Weedon kept the head and a number of personal objects Osceola had given him. Later, Weedon gave the head to his son-in-law Daniel Whitehurst. In 1843, Whitehurst sent the head to Valentine Mott, a New York physician. Mott placed it in his collection at the Surgical and Pathological Museum. It was presumably lost when a fire destroyed the museum in 1866. Some of Osceola's belongings are still held by the Weedon family, while others have disappeared.  Captain Pitcairn Morrison sent the death mask and some other objects collected by Weedon to an army officer in Washington. By 1885, the death mask and some of Osceola's belongings had arrived in the anthropology collection of the Smithsonian Institution, where they are still held.  In 1966, Miami businessman Otis W. Shriver claimed he had dug up Osceola's grave and put his bones into a bank vault to rebury them at a tourist site at the Rainbow Springs. Shriver traveled around the state in 1967 to gather support for his project. Archaeologists later proved that Shriver had dug up animal remains; Osceola's body was still in its coffin.  In 1979 the Seminole Nation of Oklahoma bought Osceola's bandolier and other personal items from a Sotheby's auction. Because of the chief's significance, over time some people have created forgeries of Osceola's belongings. Rumors persist that his embalmed head has been found in various locations.

Did Weedon keep the mask?
For some time, Weedon kept the head and a number of personal objects Osceola had given him.