A box truck hit and injured two pedestrians before slamming into an occupied car in San Francisco on Monday afternoon, according to the San Francisco Fire Department.

About 3:45 p.m., a total of seven people were injured, two of them seriously, after the box truck plowed into two elderly men on a sidewalk and then into a vehicle with five occupants at Geary Street and 21st Avenue, fire officials said.

The box truck driver apparently was trying to make a U-turn, possibly changed his mind mid-turn and hit the two men, ages 66 and 79, officials said. The truck driver then hit the car carrying a family of five.

Heather King saw the truck hit the two pedestrians on the sidewalk on Geary and then head straight for her car. Her husband was behind the wheel, and her three kids were in the back seat.

"I just saw him hit two guys," she said. "Barely saw one guy, but the other I saw fly several feet through the air. ... Right where the truck hit (her car), my 10-year-old was sitting. Luckily, just glass hit his face."

The driver was delivering frozen food to a restaurant, police said. Video evidence shows him appearing to make a wide right turn onto Geary, but then he changes direction and heads across Geary.



A homeland security employee happened to be at the scene and made a citizen's arrest, holding the truck driver until police arrived, official said.

The two pedestrians were taken to a trauma center, and one of them had life-threatening injuries, fire officials said. One was being treated for a punctured lung, and the other was undergoing surgery for internal bleeding, officials said.

King and her family were evaluated at the scene, they said. None of them was seriously hurt.

The crash was under investigation, and officials were asking the public to avoid the area.

NBC Bay Area's Jean Elle contributed to this report.