(AP) Military officials say a Marine who shot two of his colleagues to death and then killed himself at a Virginia base was a tactics instructor who joined the corps seven years ago.

The Marines said Saturday that 25-year-old Sgt. Eusebio Lopez gunned down 19-year-old Lance Cpl. Sara Castromata and 23-year-old Cpl. Jacob Wooley on Thursday in barracks at the Quantico base near Washington.

Lopez, of Pacifica, Calif., was a teacher at a school that tests Marines who want to become officers and his specialty was machine-gunner. Castromata, of Oakley, Calif., was a warehouse clerk for the school. Wooley, of Guntown, Miss., was a field radio operator and also worked with the school.

The Marines have not described the relationship between the three or released a motive for the shooting.