A former University of South Florida student has been charged with murder in the deaths of two missing doctoral students after one of them was found dead this week. Hisham Abugharbieh, 26, has been charged with two counts of first-degree murder in the deaths of his roommate, Zamil Limon, and Limon’s friend, Nahida Bristy, both 27, who were reported missing shortly after they were last seen on April 16. Limon’s body was discovered Friday morning on the Howard Frankland Bridge, which spans Old Tampa Bay between Tampa and St. Petersburg, about 20 miles from his off-campus home near the university, according to Hillsborough County Sheriff’s Office Chief Deputy Joseph Maurer. Bristy remains missing, and marine and dive teams have been searching the waters near the bridge.…