In the fall of 1859 there took place in the town of San Bernardino a difficulty of local origin, that had somewhat the aspect of a civil war on a small scale. There were in the place two rival physicians, Dr. Ainsworth and Dr. Thomas Gentry. They met one day at a livery stable, and Ainsworth returned fire on Gentry, who fled, and sent word to his friends at El Monte that he was “corralled by Mormons.” Impartial testimony on either side goes to show that the affair was purely personal, and that no faction or party question was concerned. But Gentry’s friends at El Monte rallied to his summons, and, led by a rough named Frank Green, they set forth, 100 strong, prepared to capture the town if necessary. On arriving at San Bernardino, and learning the circumstances, as they actually existed, the more rational of the invaders, comprising about one-half of the -party, returned home, but the rest remained, being in a frame of mind disposed toward disorder. Ainsworth and his friends had entrenched themselves in an old adobe house on the corner – west of the South Methodist Church. As night came on, with no indications of the approach of the hostile party, the to-be-besieged, who were well armed with rifles and revolvers, went forth and dispersed themselves over the cornfield surrounding the house. It was not until a late hour that Green’s gang was seen approaching the house, upon which all the party of defense lay down, leveling their guns upon the enemy. The party from El Monte formed in line of battle on the opposite side of the road as quietly as possible, but they retreated in confusion and disorder on perceiving that they were under the eyes and the guns of the foe. As a body they were demoralized, but certain individuals remained and caused some disorder and bloodshed. Jim Greenwade, Frank Green and the Sea brothers were thus persistent, Green shooting David Coopwood in the thigh. The ruffian Green was bravely attacked in his turn by Taney Woodward, and the two men emptied their pistols at each other at short range.
This fracas took place September 21, 1859. For days thereafter San Bernardino was a scene of lawless disorder. There were United States troops encamped on the banks of the Santa Ana river, three miles from town, but they did not interfere, probably because they were not called upon by the civil authorities. The sheriff was powerless to quell the mob, until at last he made a general call for all citizens to unite and drive out the intruders. This being done, peace and quiet, law and order, prevailed for a long time after.
Green subsequently met a violent death at El Monte, slain by a man whose father he had killed.
Source: An Illustrated History of Southern California: embracing the counties of San Diego, San Bernardino, Los Angeles and Orange, and the peninsula of lower California.