The duel came from a letter published in a newspaper. It seems that Casella was challenged by Marnold.  In the course of the duel Marnold was wounded and the duel was ceased by the director who felt the wound had put Marnold in a position of inferiority.

Newpaper Accounts
*another duel is reported in these papers as well that is quite entertaining.

THE LINCOLN EVENING NEWS MONDAY, NOVEMBER 21, 1910

San Francisco Call, Volume 108, Number 180, 27 November 1910
It grew out of a letter published in a royalist newspaper. Marnold was wounded, in the sword arm. Then Rouseier Dorcierres, the director of the duel, who has served in that capacity for more than 100 “affairs of honor,” declared that Marnold was in a condition of inferiority, and refused to allow the duel to proceed.

The Frederick Post, Page 6, December 10, 1910
In the second duel ,which closely followed the first, Mons. Georges Casella was called to the field of honor bv Mons. Marnold, who felt offended