The mass killing in California last weekend has turned the spotlight on the online world of "pick-up artists" - and anti-"pick-up artists".
There was a storm on Twitter when Elliot Rodger's misogynistic ramblings and videos were discovered online. Bloggers and commentators pointed out he used language familiar to the "pick-up artist" (PUA) community - an industry dedicated to teaching men the art of attracting women.
The idea of men trying to pick up women is nothing new of course, but the PUA community has developed highly structured rules, supposedly based on psychology, which pick-up gurus claim will lead to unprecedented sexual success.
"I take a guy who - if he met a lady in a bar or saw someone on the street - he wouldn't know what to do. Or if he did try something, it would fail," Richard La Ruina, owner of PUATraining.com told BBC Trending. "We teach him how to interact with women... and give him the confidence and ability to date women."
The community was popularised by the 2005 book The Game: Penetrating the Secret Society of Pickup Artists by Neil Strauss, which details the author's adventures in the PUA world. And it has since become big business online with hundreds of books, DVDs and pick-up coaches offering to teach men the latest tricks - for a price.
There's been debate about whether the PUA industry is anti-women, and attitudes towards the opposite sex vary widely among coaches and PUA followers.
But the movement has also has spawned an extreme offshoot - the world of anti-"pick-up artists", some of whom blame their lack of success with women on both the PUA industry, and the women themselves.
One anti-PUA site, PUAHate.com, ostensibly warned men away from "pick-up artist" gurus out to make money. It became a magnet for misogynistic rants by Elliott Rodger and others, and was taken down after the attack in California.
"I went on the website and signed up for the forum to get a deeper feeling of what this community was about," says journalist Patrick Kearns, who has written about PUAHate. "And you just see deeper and deeper layers of misogyny that pile up through all the forums."
One thread he found asked: "Are ugly women completely useless to society?" Others suggested that fat women should be prevented from leaving the house until they reached a healthy body-mass index.
Kearns interviewed one of the site's administrators and actually found his views to be at odds with most of the site's users. "He was trying to do a good service, but just let it get out of hand," says Kearns. "This website was created to say these things won't work for you guys - don't waste your money, stay away from them."
Immediately after the shootings some posters to PUAHate distanced themselves from Rodgers, but others sarcastically commented that the shootings could have been prevented if only women had had sex with him. "Again it seems like it's deflecting the blame onto women," says Kearns. "After spending a good amount of time in the forum and reading some of the threads, really nothing surprises you."
Reporting by Mike Wendling