SAN DIEGO—A driver plowed through a crowd on a sidewalk under an overpass with homeless tents on a rainy Monday morning in downtown San Diego, killing three people and injuring six others, including two who are hospitalized in critical condition, police said. The driver—whom authorities identified only as a 71-year-old man—appeared to lose control of his Volvo station wagon shortly after 9 a.m. near a community college, said San Diego Police Chief David Nisleit. He was arrested on suspicion of driving while impaired. “For whatever reason, (the driver) veered to the right, went up on the sidewalk, struck multiple pedestrians there and then came back on to the roadway,” Nisleit said. Three people died at the scene. Five of the six others who were injured were taken to hospitals, authorities said. Nisleit offered “my deepest condolences,” to the families of those who died. The sidewalk had tents on it. Nisleit …