LAS VEGAS (AP) - The FBI says investigators found no manifesto, video, suicide note or other communication from the gunman behind the 2017 mass shooting on the Las Vegas Strip.

  

Findings from the FBI's behavioral analysis unit released Tuesday show several potential factors that may have driven him to unleash a hail of gunfire on the crowd at a country music festival.

  

Investigators believe gunman Stephen Paddock became increasingly distressed and intolerant of stimuli as he aged and as his physical and mental health declined, his suicide after shooting at the crowd was a key aspect of his attack.

  

Investigators say Paddock also showed minimal empathy in his life and his decision to murder people while they were being entertained was consistent with a cruel personality and history of manipulation and duplicity.