Officers responded to a report of an accident in a parking lot at 845 Embarcadero at about 4:15 p.m., Officer Johnna Watson said.
A young boy, 2 years old, was playing in a parking lot near his mother, who was selling fruit out of her car, when the boy was run over, Watson said.
"At this time, it appears this is a tragic accident," Watson said.
The driver, only described as a man, remained at the scene and is cooperating with police, she said.
As of 6:20 p.m., police were still investigating the crash. Embarcadero, between Fifth and 10th avenues, remains closed, Watson said.