Complex sentence: Thiranagama ultimately left the group, however, when she realized it was more a murderous group than a revolutionary force and was assassinated by the Sri Lankan army on September 21,1989 when she was only 35.
Split into simpler sentences: Thiranagama ultimately left the group, however, when she realized it was more a murderous group than a revolutionary force. She was assassinated on September 21,1989 when she was only 35.