The water pump pulley ‘exploded’, causing the accessory belt to fall off which drives the alternator. The pulley ‘shrapnel’ was thrown into the cooling system and damaging the hoses causing immediate loss of coolant. The loss of electrical power due to the alternator being inoperable and the loss of cooling could have caused the vehicle to malfunction in a dangerous manner. Fortunately, the vehicle displayed an error message and was towed to the dealer without further incident.