Oregon gunman left series of letters

Police discovered Chris Harper-Mercer who had shot and killed nine people then turned the gun on himself last week. 

Police have discovered he had written a six-paged manifesto. Authorities say these may give insights into why the attack was carried out at Umpqua Community College.

Harper-Mercer's father said he is as shocked as everybody by what happened.

See snippets of what has been reportedly read out by officials.

"I was hated ever since I arrived in the world. I was always under attack. I’ve always been the most hated person in the world. Ever since I arrived in the world."

"Other people think I'm crazy, but I'm not. I'm the sane one."

"Many will ask how can they have prevented this? You can’t. You could never give me what I wanted. Nothing could have stopped it,” Harper-Mercer wrote, according to People. “What was supposed to happen? What great event was supposed to make me realize I had so much going for me?”

"I’ve been forced to align myself with these demons and become one of them,” he wrote. “At first, it was involuntary, but now I am aligned with them. I now serve. When I die I will become one of them."

"My success in Hell is assured."

Meanwhile, US President Barack Obama is set to visit the site of the incident and the families of the victims.