A three-year-old girl accidentally shot and killed her four-year-old sister Sunday night at an apartment in Houston, Texas.

The incident was reported shortly before 8 p.m. local time, Harris County Sheriff Ed Gonzalez said at a news conference. 

The two girls and five adults, all of whom were family and friends, were spending time at an apartment on Bammel North Houston Road near Tomball Parkway when the shooting occurred.

According to Gonzalez, the girls and their parents lived at the apartment.

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Harris County, Texas cruiser

A three-year-old girl accidentally shot and killed her four-year-old sister Sunday night in their apartment in Houston, Texas. (Harris County Sheriff's Office/Facebook)

The girls were left in a bedroom by themselves at one point during the night because one parent believed the other was watching them. The three-year-old then found a loaded pistol and shot once, striking her sister, Gonzalez said.

The four-year-old girl was pronounced dead at the scene.

Family members heard the shot fired and rushed to the bedroom, secured the firearm and reported the incident to authorities.

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HCSO squad car file

The three-year-old found a loaded pistol and fired one shot, which killed her sister. (Scott Halleran/Getty Images)

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It is unclear at this time if any charges will be filed in connection with the shooting.

The incident remains under investigation.