So, person known to mental stability problems,
Gun acquired through private transfer, no background check required

“…the family friend, Madison Davey told the TV station…”I always knew something would happen. I never thought she would do this. Christy was toxic for the family. She was mentally unstable.”…

…Sheats used the same gun in the shooting that her great-grandfather had left for her with instructions to “protect her family.” The “completely off-the-wall emotional” mom once spent time in a mental institution, Davey said…”

Texas woman who killed her two daughters told her husband: “This is about punishing you” https://t.co/ri8XAXr4Gm pic.twitter.com/eyRVf4JwUC

— New York Daily News (@NYDailyNews) June 28, 2016