USF doctoral students vanish; family says disappearance is 'very suspicious' and 'unusual'

Limon, a USF doctoral student pursuing a degree in geography and environmental science and policy, was last seen at his home around 9 a.m.

Bristy, a USF doctoral student studying chemical engineering, was last seen around 10 a.m. on the USF Tampa campus at the NES Building.

A family friend notified police April 17 at approximately 4:50 p.m. after concern grew over being unable to contact Limon and Bristy.

Both have since been added to the state and national missing persons databases, police said.

"He is a very responsible and punctual person, and that's why the situation is so unpredictable and unusual to us … like, and very suspicious," Zubaer Ahmed, Limon's younger brother in Bangladesh, told the outlet.

"We're in deep pain, and [it's a] devastating situation."

Ahmed said Limon and Bristy were discussing potentially getting married in the future but were focused on their education.

"Another important point that is they talked about having a future together, but they are not that serious about it. Both of them are thinking about whether we can marry together, and they are discussing that," he said.

USF Public Information Officer Larry McKinnon told FOX 13 that "no stone would be left unturned" in the search for Limon and Bristy, though authorities see no signs of foul play.

"Everybody internally is obviously very concerned, as we are concerned. It's not typical of their behavior. They're graduate students," McKinnon said. "We don't have information that there is foul play or suspicious nature at this point.

"When we get to this point where we aren't having success in locating them, then our next best source is the public. That's where we are at," he said. "Everybody's hoping for a positive outcome on this. And that's why we're taking it very seriously and making sure we leave no stones unturned to try to find them."

Fox News Digital has reached out to the Hillsborough County Sheriff's Office and USFPD for additional information.