Son of William Gardiner and Susanna Pickard of England.
Mounted Guard Gardiner was shot and killed in the Upper Valley of El Paso County, Texas. He and several other officers noticed a suspicious wagon being driven along a road by two men. The officers stopped the wagon, and as they advanced the suspects opened fire and fled. Gardiner and another officer were wounded in the initial round of fire. The officers returned fire as the suspects waded across the Rio Grande River and escaped into Mexico. Several sacks containing 12 bottles of tequila were found in the wagon. Both wounded officers were taken to the hospital, where Gardiner died on Saturday, October 21, 1922, at 5:00 a.m. Gardiner was survived by his wife and children. He had served with the agency for four years and he was buried in Concordia Cemetery in El Paso, Texas.