The incident happened about 11 a.m. Saturday as two events took place at the Boise Spectrum, a complex of movie theaters, shops and restaurants.
Witnesses told police the Porsche and some other drivers were "kind of showing off for the crowd" as they left the parking lot where the event is held and the driver lost control going too fast, LeBar said.
Eyewitness video of the incident showed the Porsche spinning sideways before striking pedestrians. Amid screams from bystanders, people can be seen attending those injured as some followed the driver as he walked away from the scene. The victims sustained serious but not critical injuries, said Boise Police Lt. Charles LeBar, according to the Idaho Statesman.
Tom Weekes of Boise attended the event with his 12-year-old son and had just moved a few feet back on the sidewalk when the vehicle lost control. "There was a group of kids to the right of us and he hit every one of them".
A crash reconstruction team was working at the scene just after noon.
Police say the driver, who was not injured, is cooperating in their investigation. "You could hear the screaming", he told the AP.
Boise Police say that while the investigation is ongoing, preliminary information shows that the driver of the Porsche was accelerating rapidly as he left the auto show onto eastbound Overland Road, lost control, and ran into the crowd. Hundreds showed up to view the unique cars on show and engage the drivers. Police will forward information to the Ada County Prosecuting Attorney's Office when the investigation is completed.
Six victims were transported to an area hospital by ambulance, and five were taken by private vehicle.
"People like to show off when they leave these events", he said.