It's the question on many people's minds as new details come out on the young man behind the Isla Vista rampage: Could he have been stopped?
According to Santa Barbara County Sheriff Bill Brown authorities couldn't hold alleged murderer Elliot Rodger after they were called to check on him by family members as "he did not meet the criteria for 51.50 of the welfare institutions code..."
However, just hours before his rampage in Isla Vista Friday, Rodger emailed his parents his 140 page manifesto and posted a video entitled "Retribution" to YouTube sharing his deadly plan.
The 22-year-old then stabbed three young men in his apartment to death: those men have been identified as: 20-year-old James Cheng-yuan Hong, 19-year-old George Chen, and 20-year-old Weihan Wang.
All were from the Bay Area and were students at UC Santa Barbara.
Rodger then shot and killed Tri Delta sisters Katherine Cooper and Veronika Weiss then Christopher Martinez outside of a deli.
Tonight a vigil will be held at Westlake swimming pool for 19-year-old Weiss as the community continues to mourn.
Surveillance Video Shows Moment of Attack
Surveillance video from a convenience store hit in Friday's Santa Barbara shooting shows the moment Rodger opened fire on the building. The video captures the tragedy of the massacre as it began to unfold.
The Video - "Retribution"
Before setting out on a terrifying rampage that left six people dead Friday night, Rodger made an ominous video that left little doubt about what he was planning to do.
"Well, this is my last video. It all has to come to this. Tomorrow is the day of retribution. The day in which I will have my revenge against humanity," Rodger said in the video.
In the nearly seven-minute long rant entitled "Retribution," Rodger speaks angrily about being rejected by multiple women for love and sex for years, and says that he will, quote "punish you all for it."
Rodger's bloody assault in the college town of Isla Vista, California came to an end when he took his own life.
WARNING: Video may be disturbing to some.
Police Radio Calls Released
Emergency radio calls are being released that reveal how first responders reacted to Friday night's murder rampage in Santa Barbara.
Law enforcement personnel are also heard describing how Elliot Rodger ran down two people riding bikes as he drove his BMW.
Authorities are heard on the recordings saying Rodger had been shot.
Where did Rodger Get the Weapons?
As the investigation continues, police are looking at a local gun shop.
Officials say UCSB gunman Elliot Rodger had three semi-automatic handguns and 400 rounds of ammo in his car, after going on a deadly stabbing and shooting rampage.
Law enforcement sources say Rodger purchased one of the handguns at Gun World in Burbank.
Detectives served a search warrant there yesterday and are going through records as part of their investigation, but say the guns had been purchased legally.
In his 141-page manifesto, Rodger is full of hate and loathing -- of himself and others. He details everything from his plan for slaughtering popular sorority girls to his own suicide.
In the manifesto, Rodger said police visited his home last month and that he had, "the striking and devastating fear that someone had somehow discovered" what he was planning to do. He also said that if police had searched his room, they would have found all his weapons and writings about his plot.
Rodger went on to say that videos he posted online had alarmed his mother and he believed she or a mental health agency had asked authorities to check up on him. According to Rodger, the police left after he told them it was all a misunderstanding.