On May 16, 1903, Probationary Officer McCartney was on patrol near the cracker factory at 14th Street and Clark Avenue when a mob attacked him with pistols, bricks and razors. While struggling to protect himself he was able to shoot and kill one of the suspects. He was shot in the abdomen and succumbed to his wounds 15 days later on May 31, 1903. Warrants were issued for two male suspects in regard to Officer McCartney's death.

Officer McCartney had been with the agency for only two months and was survived by his wife, Mary, and three children. Interred: Calvary Cemetery, St Louis, MO.