The collision was reported around 2:30 p.m. at Market and Beale streets, police spokesman Officer Carlos Manfredi said. The truck driver stopped at the scene and is cooperating with investigators, he said.
A witness at the scene who declined to give his name said that as he was waiting to cross the street, he saw the truck hit the victim as the victim crossed Beale Street in a crosswalk.
He said paramedics administered CPR but to no avail.
As of 4 p.m., the victim's body was still on Beale Street near the crosswalk, covered by a yellow tarp. A gray baseball cap and a tan Velcro sneaker had been placed on the edge of the tarp, and a matching sneaker was resting in the middle of Beale Street about 20 feet away.
Beale Street was closed between Market and Mission streets.
The truck involved in the accident, a white Dodge Ram 2500, was stopped on Beale Street and the driver, a man who appeared to be in his 20s, was sitting in the back of a police car with the door open.
Two bouquets of flowers had been left at the base of a traffic light at the intersection.