What makes the timing belt pully on camshaft shatter?

Hello, sounds like a brittle pulley. Fatigue due to weak plastic, heat, or even contamination with oil or lubricant. I'd ensure the area is totally clean before trying to install new parts. However, sounds like perhaps there may be more damage here as a result. Also, you ask a question without providing any background. In 22 years, what has been done to repair and maintain the vehicle? When was the timing belt replaced last? Use this link to find some shops near you that can help with your concern: www.repairpal.com/repair-shops