The family members of a 10-year-old in Hayward, Calif., did not report that she had been shot for more than five hours because they thought her bleeding was due to her period, police officials told the Associated Press on Friday.

The girl was hit in the buttocks with a stray bullet during a drive-by shooting on Thursday morning, and when she woke up in pain and her parents saw blood in her underwear, they presumed she had started her period, police officials told the A.P.

According to reports, the girl’s parents saw no indication that she was shot when they took her to the bathroom, as the entry wound was so small, it was easy to miss.   

Mark Ormsby of the Hayward police department told the A.P. that they found out that she was hurt only when she woke up for school the next morning and said she was in pain. The girl and her parents were unaware that a bullet was lodged in her pelvic area, and they only learned about the shooting when they inspected the girl’s bed and found bullet holes in them.

A full body inspection of the girl showed a small entry wound, and emergency services were immediately called.

The girl was hospitalized and had surgery to remove the bullet. She remained in stable condition as of Friday.

The motive behind the shooting is still unknown, and no arrests have so far been made. According to reports, investigators believe the occupants of the house were targeted due to a case of mistaken identity.

The shots were fired at about 2 a.m., and it wasn’t until 7.30 a.m. that the shooting was reported to the police, Ormsby told ABC 7.

"We're unaware of why we were just getting the phone call a couple of hours later. If they know shots are fired and you know that your child has been hit, that would be something that I would absolutely say you have a responsibility to call the police," Ormsby said.