Back trouble and brain fog bothered suspect in UnitedHealthcare CEO killing, his posts show

Investigators have uncovered evidence that Luigi Mangione had prior knowledge UnitedHealthcare was holding its annual investor conference in New York City.

Investigators are working to piece together why Luigi Mangione may have diverged from this path to make the violent and radical decision to gun down UnitedHealthcare's CEO.

Days after UnitedHealthcare CEO Brian Thompson was killed in a dawn ambush, the gunman was still at large and the reason for the killing remained unknown.