SUNNYVALE, Calif. — A former Army sharpshooter with a history of post-traumatic stress disorder plowed his car at high speed into a group of pedestrians in a Silicon Valley suburb, injuring eight people, then told authorities that he intentionally hit them, police said.

Isaiah Joel Peoples, 34, gave no indication why he targeted the group in Sunnyvale, California, authorities said. He was charged Thursday with eight counts of attempted murder. Four of the pedestrians remained hospitalized, including a 13-year-old girl who was in critical condition. Peoples was jailed without bond and scheduled to appear in court today.

A witness said he watched in horror as the car sped through a crosswalk in a shopping area Tuesday evening and bodies went flying. It was a warm night, around dinnertime, and people were out in cafes and restaurants.

“I saw this woman fly through the air right in front of me. She flipped upside down and then fell right in front of my car,” Don Draper said. He marched over to Peoples’ car, which had swerved onto a sidewalk and crashed into a tree. He said Peoples did not appear drunk but looked dazed and was mumbling over and over, “Thank you, Jesus. Thank you, Jesus.”

Sunnyvale Police Chief Phan Ngo declined to discuss details of interviews with Peoples and said police are still working to determine his motivation.

“When we took him into custody, he did not behave in any manner that would be considered bizarre,” Ngo said. “He has not shown any remorse.”

Though the FBI was assisting in the investigation, there was no evidence linking Peoples to any terrorist organization and, so far, no evidence of a federal crime, said Ngo, who said Peoples had picked up food and was on his way to deliver it to his Bible study group.

Investigators were processing evidence found Wednesday in a search of Peoples’ apartment in Sunnyvale, about 50 miles (80 kilometers) south of San Francisco. Police also gave him a blood test for drugs and were checking into accounts from family members that he had a history of mental illness.

Family and friends described Peoples as quiet and polite and expressed shock at his involvement.

His mother, Leevell Peoples of Sacramento, said she could not imagine any situation in which her son would deliberately crash into innocent people other than something related to the PTSD she said he experienced after serving in Iraq.

“Unless the car malfunctioned, he would not have done that. He’s like the perfect, model citizen,” she said.

Her son graduated from Sacramento State University after returning from Iraq in 2007 and was working as an auditor for the Defense Department in nearby Mountain View, she said.