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