mohammed emwazi jihadi john
Islamic State group militant Mohammed Emwazi, who was identified this week as "Jihadi John," the ISIS militant who has appeared in videos beheading hostages. Emails between Emwazi and a British journalist reveal his anger at the UK security services. Getty Images

A series of emails sent to a journalist by Mohammed Emwazi laid bare the paranoia, anger and contradictions which may have helped lead him towards becoming one of the world's most feared and wanted terrorists -- "Jihadi John".

In 2010 and 2011 Emwazi emailed the Mail on Sunday's security editor Robert Verkaik to complain about what he described as persecution by the British security services -- MI5.

In one email Emwazi claims when he tried to sell a laptop online, he was contacted by someone who said he'd buy it without even testing it. He began to suspect the buyer was a secret agent.

"When I sell anything via internet I always only write my surname in the ad," he wrote. "That person to my surprise didn't even bother looking to see of the laptop works or not!!! (when you buy something, from someone you've never seen before you most likely would test the product!!)...

"Anyway, in a matter of seconds, I gave him the laptop (thinking that he's going to test the laptop) & he gave me the money straight-away... We 'shacked hands' & he said 'nice doing business with you Mohammed'. I NEVER TOLD THIS PERSON MY FIRST NAME!! & I NEVER GIVE OUT MY FIRST NAME!! IT WAS IMPOSSIBLE FOR HIM TO KNOW MY FIRST NAME!!"

Emwazi told Verkaik that sometimes he felt like a "dead man walking", and appeared to be fearful for his own safety. "Sometimes i feel like im [sic] a dead man walking, not fearing they may kill me. Rather, fearing that one day, I'll take as many pills as I can so that I can sleep for ever!! I just want to get away from these people!!!"

The charity Cage -- which said Emwazi was "extremely gentle, kind" and a "beautiful young man" -- suggests it was partly as a result of pressure from MI5 that Emwazi became radicalized, claims angrily denied by U.K. Prime Minister David Cameron.

Cameron's official spokeswoman said: "It is completely reprehensible to suggest that anyone who carries out such brutal murders -- they are the ones responsible and we should not be seeking to put blame on other people, particularly those who are working to keep British citizens safe," she said.

From what friends have said about Emwazi, he could be kind, and even humorous. In one email to Cage he writes: "Smile, it's me again?! Sorry for the headaches I cause..."

Yet Emwazi was also allegedly a member of Al-Qaeda 'sleeper' cell 'The London Boys' and a member of a group of robbers who used Tasers to target victims in London's wealthy Belgravia district. However there is still no real explanation of what drove a confused, intelligent young man to become one of the world's most merciless killers.