Montreal, Canada - Mohammad Nazemi struggled to find the words.

Huddled amongst more than 150 mourners to commemorate the victims of this week's deadly plane crash in the Iranian capital, the 25-year-old computer science student said two of his friends were on the flight that went down.

"I don't know, what should I say?" Nazemi told Al Jazeera at the vigil outside Concordia University in downtown Montreal on Thursday evening.

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"It's hard. It's hard to think that they're [people] that you knew and right now they're not alive any more."

At least 63 Canadian citizens, mostly of Iranian origin, were killed when the Ukrainian International Airlines flight went down in Tehran on Wednesday, killing all 176 people on board.

Many other passengers, including several Iranian students attending Canadian universities and colleges, also had ties to Canada, local media has reported.

Nazemi said two of his friends' relatives were also killed in the crash.

Video appears to show Ukraine plane being hit (2:58)

"I don't care about the reasons that this situation happened," he said, tears in his eyes. "All I care [about] is that our loved ones are not with us any more."

Zohreh Mosaferi also lost her friend, Shadi Jamshidi, in the crash.

The two women met at university in Tehran in 2006, Mosaferi said, and they both ended up in Canada.

"The first thing that comes to your mind is that a life ahead of a young girl was taken away from her," said Mosaferi, who held a large picture of Jamshidi during the commemoration.

Jamshidi "tried to enjoy every second of her life", Mosaferi told Al Jazeera.

"She wanted to live. Travelling, music, trying new stuff in her life. She was … I don't know," she said, her voice breaking.

Calls for investigation

The deadly crash came amid heightened tensions between Iran and the United States, which assassinated top Iranian military commander Qassem Soleimani early on January 3.

Many other passengers, including several Iranian students attending Canadian universities and colleges [Jillian Kestler-D'Amours/Al Jazeera]

In response to the killing, Iran launched several missiles at an Iraqi military base used by US forces in Anbar Province and near the US airbase in Erbil.

Canadian Prime Minister Justin Trudeau said on Thursday that Canada had obtained intelligence that indicated that the Ukrainian plane was shot down by an Iranian surface-to-air missile.

"This may well have been unintentional," he said during a news conference in Ottawa.

Tehran had earlier dismissed reports that an Iranian missile downed the plane as "illogical rumours".

Trudeau called on Iran to allow Canada to help conduct a thorough and credible investigation into what happened.

The Ukrainian passenger jet carrying 176 people went down shortly after takeoff from the Iranian capital's main airport [Ebrahim Noroozi/AP]

He also stressed that Canada could not assign any blame before such a probe takes place.

"Right now, our focus is on supporting the families that are grieving right across the country and providing what answers we can," he told reporters.

Community united

Several events have been organised across Canada this week to remember the victims.

"The whole Iranian community is united," said Saman Abolfathi, a member of Concordia University's Iranian Student Association, which organised the vigil in Montreal.

"It's hard for us. We are all shocked. We are speechless."

Abolfathi, who came to Canada last year to study psychology, told Al Jazeera that he and several of his friends are grappling with the thought that it could have been them on that flight.

"I couldn't believe it at first," said the 22-year-old student.

Saman Abolfathi, a member of Concordia University's Iranian Student Association, was among those who attended Thursday's vigil for victims of the deadly incident in Tehran last Wednesday [Jillian Kestler-D'Amours/Al Jazeera]

"I was going through the news and I was like, 'What? Why? Why [has] this happened?"

He said he hoped Canada could help investigate the crash, and that the details of what happened would help the victims' families cope.

In the meantime, people continue to share memories of the loved ones they lost.

Azadeh Jazaherpour described her friend Sara, who was also killed on the plane, as kind and light-hearted.

She "could make friends in a blink of an eye", said Jazaherpour during the Montreal vigil.

"We will never forget her beautiful smile and laugh."