UPDATE 3:30 p.m. Karageorge's sister, Sophia, told the Columbus Dispatch her brother was last seen at his E. 7th Avenue apartment at 2 a.m. Wednesday before leaving to take a walk.

“He had some extenuating circumstances that night that lead us to believe he was upset,” she told the paper.

Sophia Karageorge said her brother has suffered from a history of concussions.

“We’re very concerned that he’s not himself and that he maybe doesn’t know what’s going on,” she told the Dispatch. “Every time he’s had a concussion, he’s been evaluated and listened to his trainers. He’s been properly taken care of by OSU the entire time he’s been an athlete for them. But ... his repercussions from them have been long-term or delayed later after the factor.”

Ohio State walk-on defensive lineman Kosta Karageorge has gone missing, according to his parents early Thursday morning.

Kosta was last seen around 2 am November 26. His family is asking for prayers & any info regarding his whereabouts.Please call: 614-747-1729 — KostadinosKarageorge (@kostadinos81) November 27, 2014

Karageorge, a fifth-year senior and former member of the wrestling team, did not show up to the team's Thanksgiving Day practice, according to his mother. She added in a Facebook post that his phone was last tracked at 2:30 a.m. in the Grandview area.

Ohio State football player Kosta Karageorge is missing, per his mother. Please spread. pic.twitter.com/FTeaK4sVZf — Eleven Warriors (@11W) November 27, 2014

Columbus Police confirmed to NBC4's Jerod Smalley they were indeed searching for Karageorge.

Columbus police confirm they are looking for Kosta Karageorge. — Jerod Smalley (@JerodNBC4) November 27, 2014

Ohio State did not immediately respond to request for comment.