The victims were struck just before 1 p.m. PST, when a vehicle drifted across three lanes, hit a utility pole and then rammed into a bench at the bus stop, Officer Bryan Galbreath said.
The driver of the vehicle was treated for minor injuries and then taken to a police station for question, the Riverside Press-Enterprise reported.
Police have not released the names of the victims. The two who died at the scene were identified as a woman and a female minor, and the two who were taken to Riverside Community Hospital with severe injuries were identified as a woman and a man.
Galbreath said there was no indication that speed or alcohol or drug impairment were factors in the crash.