An autopsy reveals a Plano teen was on anti-depressants when he killed his family inside their home last month.
McCann Utu, 19, called 911 after stabbing his mother, 45-year-old Stacy Fawcett, and his 17-year-old brother Josiah. He then took his own life, police said.
About 2,000 people gathered at a memorial service for the woman and her sons last month.
Relatives blamed his actions on two head injuries. Utu's brain is now being studied at UT Southwestern Medical Center.