NEW : School 's president : `` These are just kids who did very , very stupid things '' NEW : Campus police chief : " I'm not sure what to do with these people. Police interview one `` person of interest , '' search for another . Federal authorities ATF , U.S. marshals lending assistance .
NEW : School 's president : `` These are just kids who did very , very stupid things '' NEW : Campus police chief : Probe indicates a student is behind the shooting . Police interview one `` person of interest , '' search for another . Federal authorities ATF , U.S. marshals lending assistance .