Investigators Provide Update in Las Vegas Shooting

With a week nearly passing, investigators are starting to form a picture of domestic terrorist, Stephen Paddock.

ABC News reports that some law enforcement officials are discovering that Paddock had severe mental illness that was likely undiagnosed.

Sources go on to tell the news agency that the portrait constructed from interviews with hundreds of people interviewed over the past week shows Paddock, though financially successful, had difficulty interacting with people. Described as standoff-ish and disconnected, he was a man who had difficulty establishing and maintaining meaningful relationships.

The 64-year-old was known for gambling in casinos for hours on end, with little or no human contact. One source told ABC News that Paddock was known to show many antisocial traits typical of past mass shooters.

On Saturday, his brother Eric shared more details about the domestic terrorist.

"He was the king of microaggression," Eric said as reported by The Independent, adding that his brother was the sole shooter behind the attack. Unlike most shooters who are usually younger, his brother was the product of decade-long experience and rumination.

On Sunday, Paddock opened fire on Route 91 Harvest festival concertgoers from his hotel suite at the Mandalay Bay Resort and Casino, killing 58 people and injuring 500 more. While the motive for the shooting remains unclear, police have said it was "obviously premeditated."