”During the mobbing one of the twins contracted a severe cold, continued to grow worse until Friday, and then died.“ — Joseph Smith1
In the aftermath of the violent attack on Joseph Smith and Sidney Rigdon, Joseph and Emma Smith's adopted twin son, Joseph Murdock Smith, got very sick. While his twin sister Julia recovered from her own illness, little Joseph's health declined due to the measles and the exposure to cold air when the mob dragged Joseph Smith outside. Tragically, he passed away a few days later, at less than a year old. Joseph Smith attributed his adopted son's death to the harsh conditions brought about by the mob's actions.2
It's unknown where the little baby Joseph was buried.