Missing Virginia Tech student remains a mystery nearly 1 week on: 'This is making sense to no one,' his mom says

Nearly one week after Virginia Tech student Johnny Roop mysteriously vanished, his mother is desperate for answers, noting that the 20-year-old disappearing "is totally out of his nature."

Authorities believe Roop left the Virginia Tech area on Feb. 16 on his own, and said there's no information leading them to believe he's in immediate danger. Authorities said he was spotted in Missouri on Wednesday and appeared to be traveling voluntarily.

"Our concern now is there's something that we're just not aware of, that mentally may have snapped. And I have no idea what that might be," Roop's mom, Veronica Widener, told ABC News on Thursday. "We just want to locate him and make sure that he's OK."

Widener described her son as a self-motivated, straight-A student. He has an "even-keeled" temperament and is passionate about his Christian faith, she said.

Roop, a senior at Virginia Tech's business school, is set to graduate this May. He completed college in three years and is looking to pursue a career in financial planning, his mom said.

Roop has been friends with his college roommates since childhood. They all grew up in Abingdon, Virginia, about 100 miles away from Virginia Tech, and Widener said her son drove home to visit every few weekends.

Widener said her last communication with Roop was via text on Feb. 14 when they exchanged "Happy Valentine's Day" messages.

She said the night of Feb. 15 was the last time someone spoke to Roop, when he went to a birthday dinner for his roommate with the roommate's parents, and his behavior appeared normal.

That night, the roommates talked about an online exam that was due the next night, and Roop mentioned that he was probably going to drive home on Feb. 16 to complete the exam from Abingdon, Widener said.

The Montgomery County Sheriff's Office said investigators believe Roop left the county on his own on the afternoon of Feb. 16. Surveillance video showed him in the Christiansburg area, which is just a few miles south of his apartment, until about 3:30 p.m., the sheriff's office said.

"Based on interviews with friends and family (in addition to video surveillance) it was noted that Mr. Roop's behavior on Friday was not consistent with his normal patterns of behaviore," the sheriff's office said in a statement Tuesday. "We have received no information leading us to believe that he is in immediate danger; however, due to the fact that Mr. Roop appears to be acting outside of his normal behavior we would like to make contact with him to confirm that he is indeed ok."

On Wednesday afternoon, Roop was spotted at a restaurant in Poplar Bluff, Missouri, the sheriff’s office said Thursday night.

Roop then drove away alone in his car, and police tried to locate him but couldn’t find him, the sheriff's office said.

"While there are many unanswered questions, based on this personal sighting, we believe Mr. Roop is acting alone and traveling on his own free will," the sheriff's office said.

"This is making sense to no one -- the measures that he's, you know, taken to just, kind of, seemingly disappear," Widener said. "Our concern at this point is whether he would be a danger to himself."

Roop drives a black 2018 Toyota Camry with a sticker of the Virginia Tech flag on the back window, the university said. The car has Virginia license plate number TXW6643.

Anyone with information is asked to call the Montgomery County Sheriff's Office at 540-382-4343.