(CNN) -- A driver hit a group of pedestrians on a sidewalk in Northern California, leaving eight people injured in what appears to be an "intentional act," authorities said.
The incident happened Tuesday evening in Sunnyvale. Police were called to the scene about 6:40 p.m., said Capt. Jim Choi of the Sunnyvale Department of Public Safety.
The preliminary investigation shows the pedestrians were on the sidewalk when the black sedan drove into them, he said, describing the accident as an "intentional act."
Witnesses told police there were no signs the car attempted to slow down and there was no evidence of braking at the scene, he said. The car eventually crashed into a tree.
All eight patients are at a local hospital, with several suffering from serious injuries, he said. The youngest victim is 13. It's unclear if the driver knew any of them.
The male driver is in custody and the incident is believed to be isolated, Choi said. Police have not identified the driver or the victims.
Sunnyvale is about 40 miles from San Francisco.