my ford falcon 2000 au made a screeching sound while I was driving it and then the serpentine belt snapped and one of the pulley type things attached to the motor also snapped off. Do you know what caused this?

Ive also been in the middle of fixing the power steering while this has happened .I replaced the high pressure hose but hadn't got around to replacing the rack boot sensor which needed to be done as the power steering is currently not working.