SAN DIEGO — A 3-year-old boy was struck by a car and killed Friday in Encanto, police said. The toddler was being watched by his 12-year-old brother when the crash occurred on Madrone Avenue near Woodman Street shortly before noon, San Diego police said. The older boy told his little brother to stay on the sidewalk while he crossed the street to get a dog, but the toddler apparently didn’t listen and went into the road, police said. The boy was struck by a green Toyota Corolla and killed. His name has not been released. The car’s 19-year-old driver reportedly left the scene momentarily but came back, said San Diego police Sgt. Ray Battrick. The crash remains under investigation.