Three boys and a girl who were feared abducted were found safe Monday thanks to an observant driver who tailed the car driven by the suspected kidnapper, a child molester.

Police found Wayne McMurtrey (search), the step-grandfather of the three boys, in a gas station parking lot after an Amber Alert (search) was issued about six hours earlier, police spokeswoman Sherry Mercurio said.

The four siblings from the Dayton suburb of Miamisburg were safe and appeared to be unharmed, police said.

A driver saw the Amber Alert on a message board posted over Interstate 70 and then noticed the car on the freeway and contacted police. The motorist continued to follow the car.

McMurtrey, 51, served nine years in prison in Arizona for child molestation, according to the Arizona Department of Corrections (search) Web site.

McMurtrey told the children's parents that he was taking them to the park, said Tim Hunsaker, spokesman for Miamisburg police department. The children were last seen around noon Sunday.

"The parents are quite ecstatic and relieved," Hunsaker told Fox News on Monday. He said the children would be taken to a hospital to be examined, but added that preliminary reports found the kids were "physically OK."

The children are Shannon Volz, 10; Trevor Skief, 6; Tyler Skief, 4; and Joseph Skief, 2.

Richard Skief said McMurtrey moved in with the family seven months ago, after he broke up with Skief's mother in Arizona. He and his wife, Mariha, said they learned from police why McMurtrey had been in prison only after they reported the children missing.

"He had never done this to me before," Mariha Skief said. "He has taken the kids out numerous times and baby-sat for them and even taken them to work with him."

Police in Columbus charged McMurtrey with receiving stolen property, and said any charges involving the children likely would come from Miamisburg.

McMurtrey was convicted in 1989 of molesting a child in Arizona, according to the Arizona Corrections Department Web site.

The Associated Press contributed to this report.