The mystery surrounding the death last week of a Schaumburg High School honor student has deepened, and now his family is offering a $10,000 reward for information that might help solve it.

"He could have been a leader. He could have been many things," said Tefera Beyene, whose son Mikias Tibebu, 18, was found lying in a road with fatal injuries early Saturday morning about a mile from his school. Beyene spoke at a police news conference Thursday at which the reward was announced, describing his son as decent, hardworking and eager to go to college.

The case of who hit Tibebu while he was out walking after leaving a group of friends has so far stymied authorities. Thursday they announced a new wrinkle in the case: They believe Tibebu — a member of his school's cross country and track teams — was lying in the road, for as yet unclear reasons, when he was struck by a vehicle.

They also have narrowed the estimated time of his death. Authorities said Beyene had called his son's cellphone about 11:30 p.m. Friday, and the teen asked to stay out longer with his friends. About 12:25 a.m. Saturday, Tibebu had separated from his friends.

By 12:38 a.m., presumably after being struck, he'd been spotted on the road by several motorists, and two nurses on their way home from work were attempting to resuscitate Tibebu, who was in cardiac arrest.

Authorities said there was no identifying debris on the road and no indication as to why Tibebu was in the middle of the road, a block away from where he strayed from his hangout and less than two miles from home. He was pronounced dead at the scene from head and neck injuries.

It's possible the teen tripped and fell while walking or suffered some kind of medical distress that brought him to the ground, Schaumburg police Sgt. John Nebl said. It's also possible that a motorist struck Tibebu while he was lying on the ground and didn't realize it, Nebl said.

Police won't get into how or why he separated from his friends but said no drugs, alcohol or fighting had been reported.

"There's been no indication of any profound impairment," Nebl said.

Authorities are checking nearby surveillance cameras but said there is no footage of the incident at that intersection.

"If we had a piece of a headlight or a bumper, then we can say, 'This was a blue car,' or, 'This came from a Ford,'" Nebl said.

The Police Department already has received some tips, and anyone with information is asked to call police at 847-882-3534.

Potential charges for the driver could include leaving the scene of an accident or reckless homicide.

"There's two different questions here. Who ran him over, and where are they? And why was he lying in the roadway?" Nebl said.

"We are looking at every aspect of his life."