5-year old dies when she and brother find loaded shotgun in neighbor's bathroom

A 5-year old girl and her brother were visiting a home near Mercedes, Texas, when the asked to use a neighbor's bathroom.  They got permission, went inside, and found a loaded shotgun in the bathroom.  Playing with the gun, the 5-year old girl was shot to death.

From the article:

Lorena Rodriguez told investigators she went to her brother’s home near Mile 11 North and Mile 2 West north of Mercedes to see him off for an out-of-town trip, according to a news release from the Hidalgo County Sheriff’s Office.

She was getting ready to leave her brother’s home about 11:30 a.m. when neighbor Rosalinda Garcia and Garcia’s two children came over to talk to her, deputies said.

Sheyla Cantu — whose name was confirmed to The Monitor by family Sunday — and her brother asked if they could use the bathroom, and Rodriguez gave them permission.

A loud bang that sounded like a firework sent the women running toward the restroom, where Sheyla lay unresponsive.

Rodriguez saw the victim’s brother standing in a doorway leading to a storage room, investigators said.

Meanwhile, Garcia picked up her daughter, put her in her vehicle and went to Knapp Medical Center with her husband.

Medical staff at the hospital pronounced her dead and a judge ordered an autopsy, deputies said.

Investigators believe the loaded .410-caliber pump action shotgun was found by the children in the restroom, Sheriff Lupe Treviño said Sunday.

The neighbors also had two children.  Why did they find it necessary to keep a loaded shotgun in the bathroom?  And shouldn't the neighbor have warned the children and their mother first?

Every gun in the hands of a child must first pass through the hands of an adult.