Officials praised the brave actions of ROTC students who confronted a gunman Thursday after he opened fire in a classroom on the campus of Old Dominion University in Norfolk, Virginia, killing one person and injuring two others. CBS News learned that one of the students in the classroom killed the gunman with a knife. The FBI identified the suspect as 36-year-old Mohamed Bailor Jalloh, a former Virginia National Guardsman who had served several years in federal prison for trying to support the terror group ISIS. Thursday's shooting is being investigated as terrorism, FBI officials said. A law enforcement source told CBS News the gunman entered the College of Business classroom, asked if it was an ROTC class, and when told yes, began shooting, killing the class instructor and wounding two others before he was "subdued" by students.…