Authorities are investigating whether a Texas teen's concussions may have affected his mental state before he fatally stabbed his brother and television-personality mother, then took his own life, police said Monday.
Police in the Dallas suburb of Plano said 19-year old McCann Utu Jr. attacked his 45-year-old mother, Stacy Fawcett, and his 17-year-old brother early Friday before stabbing himself multiple times at the family's home. Authorities said he called 911 at some point and admitted to the killings.
Plano police spokesman David Tilley said a motive for the murder-suicide remains unclear, noting that there were no witnesses to the attack and that Utu didn't leave a note. Police said they weren't aware of any past calls from the home.
Investigators are conducting interviews with family and friends who say Utu's disposition dramatically changed after he suffered a concussion during a high school basketball game in the fall of 2013, then another concussion a few months later during an altercation with another student, Tilley said.
Utu's uncle, Scott Fawcett, said his nephew's mood took a dramatic turn about a year ago, and that he was receiving psychiatric care and concussion therapy.
Doctors and researchers said there are many unknowns about the relationship between concussions and Chronic Traumatic Encephalopathy, or CTE.
"It's gonna take many more years to really find out the exact detail and all the implications involved but certainly more close monitoring on the playing field either soccer or football is certainly required and should be suggested if not mandated," said Dr. Jeffrey Cattorini, a neurosurgeon at Medical City Frisco.
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No details have been released about the type or severity of Utu's concussions or his medical history. CTE is diagnosed after death.
Sarah Stoddard, an assistant professor in the University of Michigan's School of Public Health, said an eight-year study in which she was involved indicated that young people who suffered a brain injury were more likely to engage in violent behavior. Stoddard, who isn't involved in the Utu investigation, said personality changes can result from damage to the brain's frontal lobe.
A memorial service for the family was planned for Tuesday.
NBC 5's Bianca Castro contributed to this report.