A 3-year-old US girl found a loaded gun at home and accidentally shot her sister, killing the 4-year-old, police said.

Harris County Sheriff Ed Gonzalez said the girls were in the bedroom of an apartment in Houston, where they lived with their parents.

Five adults, who were all family members or family friends, were in other parts of the apartment and the girls were unintentionally left unsupervised around 8pm on Sunday evening (local time), Gonzalez said.

“The 3-year-old gained access to a loaded, semi-automatic pistol. Family members heard a single gunshot. They ran into the room and found the small toddler, 4 years old, unresponsive,” Gonzalez said.

The girl was pronounced dead at the scene after police responded to a 911 call by the family, Gonzalez told journalists outside the home.

“It just seems like another tragic story of, again, a child gaining access to a firearm and hurting someone else and this time there was a fatal shot,” Gonzalez said.

The Harris County District Attorney’s Office will decide whether any of the adults will face charges based on the police investigation, which is still in the preliminary phase, Gonzalez said.

“Our hearts are broken. Our deputies are pretty shaken up,” Gonzalez said, noting that support personnel would be at the scene to assist the officers and family members.

“The community is impacted when a child loses their life in this way,” Gonzalez said, adding that the shooting was another avoidable gun death.

“We continue to send the message that this is very preventable,” Gonzalez said. “You’ve got to be sure you’re being a responsible gun owner, securing your weapons in a safe place. It’s got to be more than just telling young kids not to touch the weapons. You know, we’ve got to do a little more. We see far too many tragic situations like this unfold.”