Dramatic video shows a Penske box truck exploding in suburban Chicago over Memorial Day weekend.A home security camera captured video of the blast.One neighbor thought the fireworks were starting a little early, but it was a lot more than that.The driver suffered only minor injuries.He was walking next to the truck when first responders pulled up.No one else was hurt.The blast on Saturday morning also damaged four homes.Authorities determined it was an accident, likely caused by a leaking propane tank being hauled in the truck.Penske said the driver was moving household items in the rented vehicle.The company said its rental agreement prohibits the transportation of items that are explosive, flammable or otherwise hazardous.Penske said it will fully cooperate with the investigation.