Chris Harper Mercer - reportedly from the UK - entered Umpqua Community College on Thursday 1st October and began shooting at staff and students, leaving 13 dead and an estimated 20 others injured.
According to survivor Anastasia Boylan, who spoke to her family before going into hospital for spinal surgery, the gunman was specifically targeting Christians.
The gunman, while reloading his handgun, ordered the students to stand up if they were Christians, she explained.
"And they would stand up and he said, 'Good, because you're a Christian, you're going to see God in just about one second,'" her father, Stacy, told CNN, relaying her account.
"And then he shot and killed them."
Police, who raced to the scene in Oregon, USA, engaged in a shoot out with the suspect.
Mercer died in the exchange.
However it has now been revealed that, just hours before the shooting took place, an anonymous poster took to 4Chan in a bid to warn social media friends not to go to school the next day.
It said: "Some of you guys are alright. Don't go to school tomorrow if you are in the northwest."
Another post read: "Happening thread will be posted tomorrow morning.
"So long space robots
"Will post again am. 10 min countdown. Won't say more to much to prepare."
Police in Oregon, according to the Daily Star, have said they will be scanning social media for evidence.
Meanwhile, stunned celebrities have taken to Twitter to pay tribute to the victims of the shooting.
Singer LeAnn Rimes tweeted, "Reading the news about the #OregonShooting horrific! My heart goes out to the victims and their families", while Eva Longoria posted, "My hearts and prayers for those in Oregon."
Fashion designer Nicky Hilton added: "In the 274 days of 2015, there have been 293 mass shootings. Today's shooting in Oregon marks the 294th.
"This must stop".
The Oregon massacre is the latest school shooting to rock America following similar gun atrocities at Sandy Hook Elementary School in Newtown, Connecticut in 2012, and Arapahoe High School in Denver, Colorado in 2013.
Our hearts go out to the families and friends of the victims.