SMITHBORO, Ill. -- Police say surveillance video and a credit card purchase indicate that the subjects of a Kentucky Amber Alert and homicide probe were at an Illinois gas station hours after the slaying.

Authorities said surveillance tape from a Smithboro, Ill., gas station shows a man fueling what appears to be the car of slain Kentucky social worker Boni Frederick at about 7:30 p.m. CDT Monday. The man used Frederick's credit card to pay for the gas, police said.

---

Video: Police: Video Shows Car Sought In Slaying, Amber Alert

---

Police have been looking for Frederick's white Daewoo station wagon as part of a hunt for 10-month-old Saige Terrell, his noncustodial mother, Renee Terrell, and Renee Terrell's boyfriend, Christopher Wayne Luttrell, 23.

Authorities have called Renee Terrell, 33, of Henderson, Ky., a suspect in Frederick's death. Frederick's body was found Monday afternoon in Terrell's home, where Frederick had taken the baby -- who was in the state's custody -- for a visit with the mother.

Police said they believe Renee Terrell, the baby and Luttrell left in Frederick's 2000 white Daewoo Nubira station wagon, which had Kentucky license plate 675-DRV.

Amber Alerts were issued for the baby in Indiana and Kentucky. The Indiana alert was issued because Renee Terrell has relatives in that state.

Smithboro is about 50 miles northeast of St. Louis.

Arrest warrants charging Renee Terrell with kidnapping and Luttrell with probation violation have been issued in Kentucky.

Luttrell's Mother Says He Should Turn Himself In

Luttrell's mother, Barbara Hancock of Evansville, Ind., told Evansville TV station WEHT this week that he should turn himself in to police.

"He needs to give himself up and turn himself in. The baby needs to be put back," Hancock said.

Renee Terrell is described as having brown hair and brown eyes with glasses. She is 5 feet 5 inches tall and weighs 240 pounds. Luttrell is described as having blue eyes. He is 6 feet 2 inches tall and weighs 150 pounds. Luttrell also has tattoos on his arms.

Saige Terrell has brown eyes, brown hair. He is 27 inches tall and weighs 19 pounds. Police said the boy is developmentally disabled and has a scratch on the right side of his face and a rug burn on the back of his neck.

Police asked anyone with information to call 888-582-6237.