David Hassan asks himself the same question all the time, “Is there anything that I or we could have done to help Aaron out?"

He’s referring to Aaron Yoon, a London man jailed in Mauritania for his ties to terrorism. He didn’t know Yoon all that well, "I talked to him briefly a few times and he just seemed like a beautiful young man.”

Yoon had only recently converted to Islam when he started worshipping at the London Muslim Mosque, where Hassan, the former chair, met him.

Yoon was part of a group for new Muslims, active not only in sports clubs but also in volunteering for various mosque events, helping out in the gyms, doing set ups and what have you.

Hassan says Yoon and his friend Kris (Xristos Katsiroubas) stood out- a Korean and Greek kid always wearing a hoodie. Hassan tried to keep an eye out for Yoon because he knows that religious conversions can be tough for family and friends.

"When one does that they need good mentors, they need people to help them through that stage in their life," Hassan says.

He'd check in with Yoon's mentor on a regular basis - then heard that Yoon had switched to a more conservative mentor- and then that Yoon had started worshipping at the Islamic library, known to be more conservative than mainstream London mosques.

Still, the community doesn't think he picked up his radical views within those walls. They say there's no one even outside those institutions that is passing on those types of ideology.

Yet Yoon and Katsiroubas were indoctrinated somewhere and by someone. Many in the community are pointing to the third party - Ali Medlej, a Sharia Muslim that nobody can recall ever seeing at prayer or events.

By all accounts Medlej had been planning to go to Mauritania for some time.

Yoon, on the other hand, had a salesman job and was preparing to propose to a girl he was courting. He dropped it all and told his mentor he was leaving the country only two days before he headed to Africa.

Dr. Munir el-Kassem says the conversion from Londoner to terrorist has the community on alert.

"[We are] extremely concerned. Because there are people out there that are using my faith as a cover, in order to come and lure these people into something that doesn't exist."

Like martyrdom through terrorism.

A prominent imam, el-Kassem says the community is tired of being associated with those who go rogue.

"We don't want to be held responsible for the actions of terrorists who happen to be - like other terrorists who happen to be - of a certain religious affiliation."

He doesn't believe any form of militancy was learned in Canada.

"We are living in a world where a click on a button on a laptop can take us to dangerous domains.”

A secret, radical online world - that Medlej was known to frequent – and one that many believe he helped draw Yoon and Katsiroubas into.

Hassan says “This is almost like a gang, it’s not, it certainly isn't worship, it certainly isn't practicing faith.”