Those who knew Michael Zehaf Bibeau, the man who shot Cpl. Nathan Cirillo dead Wednesday in Ottawa, describe a mercurial and confounding character with a serious drug addiction.

A lifelong friend named Ahmad told CTV Montreal Friday that Zehaf Bibeau had transformed since their childhood years.

“When he was young he was a happy guy. We were always going to parties. I came back and saw that he had changed,” said Ahmad from the Montreal clothing boutique where he works.

But upon their last meeting Zehaf Bibeau only wanted to discuss religion. The choice of topic astonished Ahmad, who knew that his friend did not grow up in a religious mileu.

“I don't know what was his problem. He was not normal. He's was a normal guy before but when I saw what he did on TV I didn't understand what happened to the guy, how he flipped out and changed."

Zehaf Bibeau had lost contact with many of his friends over the last few years. His mother had barely seen him for five years and his father, believed to be living in Tunisia, was also not in close contact.

A number of media reports have suggested that Zehaf Bibeau became religious as a means to quit crack cocaine and heroin addictions.

One fellow resident of a homeless shelter told CTV News that Zehaf Bibeau’s outlook soured after being refused permission to travel to the Middle East.

“He was a real weird guy,” the man said. ”One minute he's praying, the next minute he's joking around and laughing around. Then he got real mad because he was on the no fly list. He couldn't get his passport.”

Another acquaintance told a Toronto radio show that Zehaf Bibeau was battling drug addiction and only spoke about politics once.

"He did not like Canadian and American soldiers. Someone drilled it in that young man's head that over in his homeland where his father comes from that Canadian and American soldiers were raping and killing children over there.”