University of Waterloo radicalization expert had 'extended conversations' with Aaron Driver

Radicalization expert Amarnath Amarasingamsaid he was "speechless" following the shooting death of Aaron Driver.

Driver, 24, was killed by police in Strathroy, Ont., Wednesday. Police said he was planning an attack within 72 hours in an urban centre and had recently made a "martyrdom video."

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"At the moment, I'm speechless,"Amarasingamtweeted.

Amarasingam is a post doctoral fellow at the University of Waterloo andhad spoken to Driver for his research. The most recent email he received from Driver was on April 17.

"I'm doing very well," Driver wrote. "Weather is beautiful, plenty of good frineds, work is going great. I'm always busy, which is nice. I don't like to sit around too much and waste time."

Amarasigamsaid Driver "was definitely radicalized and was not shy about his belief that the caliphate was legit."

He said Driver was "nuanced" on his views of violence and the recent violence during Ramadan and similar videos made by other "lone actors" may have led to him to go from just expressing his views to action.

Read more of his comments below.