The Phoenix Fire Department said four pedestrians, including three children all under the age of 12, were struck by a pickup truck near 19th and Campbell avenues Monday morning. Police suspect the driver may have been under the influence of drugs or alcohol. Police are taking the 22-year-old driver to a local police station for further processing. Firefighters treated and transported a 36-year-old female and her three children. The woman is in stable condition while her 7-year-old daughter is in critical condition and her injury is considered life-threatening. The woman's 11-year-old and 6-year-old daughters are also seriously injured, according to fire officials.