Patrick McCarthy, the village manager in Chatham, Ill., was at his office on Monday afternoon when he heard the wails of so many sirens in his town of 14,000 people that he knew something was terribly wrong.

When he and a co-worker rushed to the scene a few blocks away, they saw what appeared to have been a violent and inexplicable accident: A car had plowed through a field, avoiding trees and pillars, and crashed through an after-school center. Three children and one teenager, ranging in age from 7 to 18, were killed.

“Hopefully that’s what it was, an accident,” Mr. McCarthy said. “Today we’re just kind of going through and trying to figure out what do we do next after something like this happens.”

The Illinois State Police said on Tuesday that the driver of the vehicle was a 44-year-old resident of Chatham. ​The resident is not in custody, the police said, and the cause of the crash remains under investigation. Calls to the resident’s home went unanswered on Tuesday.

Toxicology reports are pending, the authorities said, adding that the crash did not initially appear to be a “targeted attack.”

In Chatham, a bedroom community about a 20-minute drive from the state capital of Springfield, residents wrestled on Tuesday with grief and horror over the crash. Y.N.O.T. Outdoors, the operator of the after-school program, was well known in town as a popular place for afternoon child care and summer camp, allowing parents with jobs to juggle work and family responsibilities.