A Minnesota man has been charged with manslaughter and child endangerment after a 4-year-old boy picked up the man's handgun and accidentally shot and killed his 2-year-old brother.

Colton Mammenga, 33, of the southern Minnesota town of Welcome, was charged Thursday, the Minneapolis Star Tribune reported.

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The shooting happened Oct. 15 as Mammenga was in a moving pickup truck with the two boys and their mother, who was in a relationship with Mammenga. A criminal complaint said a Martin County deputy pulled the truck over to the shoulder of a road and Mammenga got out holding the injured child, Matthew Alshaikhnasser.

St Paul, Minneapolis, Rochester crime

Minnesota resident Colton Mammenga has been criminally charged over the accidental shooting death of his girlfriend's two-year-old son by his four-year-old brother. (Fox News)

The boy had a head wound and died two days later at a hospital.

The charges say the 4-year-old told a deputy he got the gun from the front seat when the boys were left alone while Mammenga and the mother went inside to get something.

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Mammenga did not immediately return a call seeking comment, and online court records don't list an attorney for him. In a brief interview with the Star Tribune, the mother said, "We are still in mourning. This was a pure freak accident. We love our Mattie."