The woman was tidying up around 18 year old Joshua Prater’s room when she saw something that didn’t look right.
It had wires coming out of it and frightened the woman but not enough to keep her from taking action.
She took the device to a fire station in Phoenix where it was x-rayed and sure enough, it was a homemade bomb.
"It was something that wasn't big, but could cause serious injuries and the death of someone," cops told the Arizona Republic
The object was disabled and the home searched. Police found more bomb making materials and Prater was arrested.
Cops say they still have no idea if or when he intended to use the device but they did get one nugget of information from Prater’s parents.
They told officers friends of the boy taught him how to make the bomb.