Dozens of volunteers are searching for a Brentwood teenager who has been missing since Tuesday. Police said 15-year-old Samuel Heisel left his home sometime after midnight Tuesday.

"We're not really sure of what Sam's mindset was at this point," Interim Police Chief James McIntyre said.

Officers say Samuel L. Heisel left his Brentwood home sometime after 12 a.m. Tuesday. His car was found crashed Tuesday morning at Old Highway 79 and North Main Street in O'Fallon, Mo. It's believed the crash occurred sometime between 2 and 3 a.m. There was no one in the car, but officers did find suicide notes inside.

"We don't see any indication he was injured," McIntyre said. "The airbags did deploy."

Several agencies embarked on a search for Sam near the crash site. They used infrared technology, search dogs, and a drone.

"Very thorough," said Capt. John Neske of the O'Fallon Police Department. "Now, don't get me wrong, you could walk right by somebody in the woods and they could be three feet from you and you'd never see them."

On Thursday, volunteers led the search. Around 70 people signed up to help. Hope Bible Church served as a staging area.

"If he sees this, we love you, we want you back," Sam's youth pastor, Andrew Dickson, said.

Ted Heisel, Sam's father, is asking everyone to be on the lookout.

"Pay a little bit of extra attention when you're driving on the roads, when you're at gas stations, truck stops, restaurants, any business," he said. "We don't want to stand here and speculate about why he did this etc. but we know those facts and we're trying to rely on those facts to take us to find him hopefully alive."

Heisel is described as an Asian male, 5-foot-8, 130 pounds with black hair, brown eyes, a medium complexion and a disfigured right arm.

Anyone who has any information about his disappearance or knows where he might be is asked to immediately call 911 or the Brentwood Police Department at (314) 644-7100.

Facebook Live: Update on search for missing Brentwood teen Sam Heisel