A Northern California couple didn’t report that their 10-year-old daughter had been shot for more than five hours because they mistook her bleeding for a period, police said.

The girl was sleeping in her Hayward home around 2 a.m. Thursday when a stray bullet from drive-by shooting wounded her in the buttocks, Sgt. Mark Ormsby said Friday.

When the girl woke up in pain and had blood in her underwear, her parents thought she had started her period, police said. They also found no indication she had been shot.

Ormsby said when she woke up for school and was still in pain, her parents inspected her bed and saw bullet holes.

The girl remained hospitalized in stable condition Friday, Lt. Mark Stuart said.

Police don’t have a motive for the shooting and no arrest has been made.

Read more: Daily Mail