A 29-year-old man has been released on bail after shooting his two-year-old son with an air rifle.
Police were called to an address in Winthorpe, in Skegness, Lincolnshire, by the father, shortly before 1900 BST on Monday.
The boy was taken to Glenfield Hospital in Leicester for surgery where his condition is believed to be improving.
Officers said investigations were continuing but all indications were that the shooting was an accident.
Police said they were interviewing a number of witnesses, some of whom are children.
Det Insp Andy Wardell, from Lincolnshire Police, said: "This is being described to us as a tragic accident where a boy has been shot by his father.
"You cannot begin to guess how bad the family feels and I think it's something any parent would fear, ending up in such a situation."
An air rifle is being examined by experts, police said.