Police said the driver was trying to avert an accident as the lorry came down the hill on Monday afternoon.
Avon and Somerset Police said: “We are continuing to carry out a detailed examination of the scene in Bath, where four people tragically died this afternoon.
“The incident happened in Lansdown Lane, Upper Weston, at about 4pm when a tipper truck carrying aggregate was in collision with a number of vehicles and pedestrians.
“Three people in a car and a young girl died in the incident.
“Three other people were taken to the Royal United Hospital in Bath with minor injuries. The injured lorry driver who was also taken to the RUH, remains under observation.
“Another person was taken by air ambulance to Southmead Hospital in Bristol with serious injuries.
“Early witness accounts suggest the lorry driver was trying to avert an accident.”