The shooter — identified as Austin Wyatt Rollins, 17 — was injured and taken to the hospital, where he died, officials said.
The bomber is believed to have mailed two packages from a FedEx drop-off center in Austin, the source added.
Suicide deaths have been increasing in the U.S. and are the third leading cause of death among teenagers.
The Minneapolis police officer who fatally shot Justine Damond is now behind bars and charged with third-degree murder and second-degree manslaughter.
As lawmakers across the U.S. predict that sports gambling will soon be legal, sports organizations and others are convinced that doing so would be a bad bet.