Glen Rock, Pa. ? A dump truck that lost control while driving down a steep hill slammed into parents and children at a school bus stop, killing a woman and her daughter and critically injuring two other children.

Authorities were still investigating Friday afternoon’s multiple-vehicle crash, but police chief Jim Childs said it appeared the truck was too heavy to have been legally traveling on the hill.

The Blossom Valley Farms truck was carrying a load of dirt when the driver said he lost his brakes, though police did not say how much it weighed. The road’s weight limit of three-quarters of a ton.

The truck ran over a 9-year-old boy on the road and slammed into a car stopped at a stop sign, pushing the car into the intersection and leading to collisions involving three other cars, police said.

Michelle Moser, 33, and her 11-year-old daughter, Amber McAdle, whom she had just picked up at the bus stop, died at the scene.