VALPARAISO | Police say the 18-year-old whom Amanda Bach was headed to visit when she went missing Thursday night is responsible for her death.
Dustin McCowan, of 338 N. County Road 625 West in Union Township, was arrested by Indiana University police in Bloomington.
Murder charges are being sought against him, Porter County authorities said during a news conference Sunday afternoon.
Police describe McCowan as an acquaintance of Bach, whose body was found Saturday afternoon on Canadian National Railway property about 300 yards from McCowan's home.
Bach, 19, was last seen by her family when she left her Portage home to see McCowan about 10 p.m. Thursday. Her gold Pontiac was found about 3 a.m. Friday at a general store near his house. Police said the door was open and her purse was inside.
By 7:46 a.m. Friday, McCowan had posted a Facebook message about the missing woman.
"IF ANYONE HEARS FROM OR SEES AMANDA BACH CONTACT ME ... ASAP!!! THIS IS NOT A JOKE," he wrote.
McCowan arrived in Porter County just after midnight Sunday. Police believe he had been in Bloomington since Friday.
IU police took McCowan into custody at the college, where he was visiting friends on a long-planned trip, Porter County Sheriff David Lain said.
"I don't think 'hiding' is the correct word," he said when asked why McCowan was downstate. "He had a trip planned to Bloomington before (Bach's disappearance)."
Police said Bach suffered trauma to her body but didn't release details about her injuries. Officials will release a cause of death after an autopsy Monday.
Bach graduated this summer from Portage High School and "her smile lit up a room whenever she walked in," her uncle, Carlos Cespedes, said.
Police described Bach and McCowan as "school friends," though McCowan graduated from Wheeler High School.
Portage and Wheeler high school officials said grief counseling will be available this week.
McCowan is being held in the Porter County Jail.
The Bach family had not finalized funeral arrangements as of late Sunday.