A woman was arrested after her 7-year-old son accidentally shot his younger sister to death after finding an unsecured and loaded shotgun at the family’s home in suburban Denver.

Police in Westminster say the boy found the gun Tuesday morning and shot his 3-year-old sister while playing. The mother, 24-year-old Michaela Dawn Harman, was in the home at the time and has been charged with child abuse resulting in death – criminal negligence.

It’s not yet clear if she has an attorney who can speak on her behalf.

The boy and another of his younger siblings are in the temporary care of Jefferson County Human Services.

No other information was released.