ST. LOUIS – A 22-year-old man is in police custody after a 3-year-old boy located the adult’s firearm and accidentally shot himself with it.

According to Evita Caldwell, a spokeswoman for the St. Louis Metropolitan Police Department, the shooting happened around 1:20 p.m. in the 3500 block of N. 11th Street, located in the Hyde Park neighborhood.

Police say the toddler found a gun on a mattress and shot himself in the head. The child was rushed to a local hospital and is listed in critical condition.

The 22-year-old was arrested for child endangerment but has not been formally charged as of late Thursday morning.