Why Getting Answers About CTE Has Been So Difficult

The former football player who fatally shot four people and himself in Midtown Manhattan claimed to have a poorly understood brain disease, putting a renewed focus on the link between head injuries in sports and irreversible brain damage.

Shane Tamura was targeting the National Football League’s headquarters when he entered 345 Park Avenue, a skyscraper that’s also home to offices of private equity giant Blackstone Inc. and consultant KPMG. One NFL employee was injured in the shooting.