A man walking on a freeway was struck by at least one vehicle and seriously injured Thursday night in San Diego’s Grant Hill neighborhood, authorities said. Motorists began reporting a man walking on eastbound state Route 94 near the 28th Street exit a little after 7:20 p.m., according to a California Highway Patrol incident log. More than 10 minutes after the first report, a caller said the man was walking toward the 28th Street off-ramp. At 7:36 p.m., a witness reported that a vehicle — possibly a gray pickup — struck the pedestrian, who ended up on the right shoulder of the highway, according to the CHP. Several motorists stopped to try to help the victim, according to the CHP log. They described the man as elderly, with white hair. Of the freeway’s four eastbound lanes, the two right ones were blocked as drivers stopped to tend to the injured pedestrian, the CHP said. Officers classied the incident as a major-injury collision. No other details were immediately available.