2 University of South Florida doctoral students were promising young researchers. Now a roommate is charged in their killing

By Ray Sanchez, Isabel Rosales, Elizabeth Wolfe, CNN

(CNN) — Zamil Limon was last seen on the morning of April 16 at his home about three blocks from the University of South Florida campus in Tampa.

Nahida Bristy was last seen later that same morning at the Natural and Environmental Sciences building on campus.

They were both 27 and promising Bangladeshi doctoral students who started out as friends and over time developed feelings for each other — to the point they had thought about marriage, according to Limon’s brother, Zubaer Ahmed.

Limon and Bristy were reported missing by a family friend on April 17, and as days went by, their friends in Florida and relatives abroad became increasingly desperate for answers.

On Friday, Limon was found dead on the Howard Frankland Bridge in Tampa in what Hillsborough County Sheriff Chad Chronister called “a deeply disturbing case that has shaken our community.”

His roommate has been charged with killing Limon and Bristy, whose body has not been found, the sheriff’s office said.

Their loss is being felt far from the Tampa Bay area. Both students had planned to travel to Bangladesh over their summer break.

Investigators called Bristy’s family in Bangladesh to say they believed she may be dead, based on the amount of blood found in Limon and the suspect’s shared apartment, Bristy’s brother told CNN affiliate WTSP. CNN has reached out to her brother and the sheriff’s office for details.

Limon’s family told CNN they were anxiously waiting to learn what happened to the joyful, young researcher.

“It’s devastating for us,” Ahmed told CNN before his brother’s body was found Friday. “We are in deep pain.”

Limon and Bristy were among the more than 17,000 Bangladeshi students — an all-time high — enrolled in US institutions, according to the US Embassy in Bangladesh, citing the 2024 Open Doors Report on International Education Exchange.

“Please keep my beloved brother in your prayers,” Ahmed told CNN Saturday via text message.

Limon was dedicated to his environmental studies

Limon had been working on his thesis for the past two years, studying the uses of generative AI to monitor shrinking wetlands in South Florida, his brother said.

“My brother is very decent and a very simple person,” Ahmed said from Bangladesh. “He always put a smile on his face.”

He had been pursuing a degree in geography, environmental science and policy since the fall of 2024.

After completing his PhD, Limon hoped to return to Bangladesh and get a job as a university professor, Ahmed said.

“I study how natural features evolve across landscapes, with a focus on wetlands, water resources, and vegetation in both agricultural and urban environments,” Limon wrote in his student profile. His goal was “to create practical tools that enhance environmental planning, support sustainable land use, and improve long-term ecosystem management.”

His LinkedIn page said he worked as a graduate student assistant since August 2024, and his experience included stints with the Center for Natural Resource Studies, the Center for Environment and Geographic Information Services and as a junior urban planner in Dhaka. He also studied urban and rural planning at Khulna University, a public research institution in Bangladesh.

Omer Hossain, Limon’s friend and fellow student at USF, remembers him as a “chill guy” who was “always jolly.”

The two became best friends after a professor connected the two through email in the fall of 2024, Hossain said.

Later, Hossain met Bristy, who he described as an outgoing and kind person who would always include others.

Hossain says he has been in contact with Limon’s family to discuss next steps on returning his body to Bangladesh.

“The feeling is not describable for us. It’s very unexpected and shocking,” Hossain said. “Our hearts are broken.”

Bristy was ‘passionate about learning new technology’

Bristy was a doctoral student of chemical engineering at USF. She had a master’s of engineering from the Bangladesh University of Engineering and Technology and a bachelor’s of science in applied chemistry and chemical engineering from the Noakhali Science and Technology University in Bangladesh, according to her LinkedIn profile.

She was a “talented and promising student,” Professor Mohammad Ismail, the NSTU vice chancellor, said in a post on social media and the university website.

“Her untimely death is an irreparable loss to the university and the nation,” Ismail wrote.

A Facebook post from her brother, Zahid Hasan, said: “My sister is no longer with us.”

Her LinkedIn profile described Bristy as “self driven” and “skilled at problem solving, lab work and passionate about learning new technology.”

Limon had spoken highly of Bristy to his family in Bangladesh, according to his brother.

“He shared that she is a good girl, and she has a lot of talent, like she can sing and cook well,” Ahmed said.

Limon’s family has been anxiously following updates.

“We are becoming numb,” Ahmed said. “Anything could be possible. We just want to know the truth or what happened to them. It’s not possible that two students disappear out of nowhere.”

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CNN’s Rebekah Riess and Nic F. Anderson contributed to this report.