Messages of shock and grief have been flooding social media, sent by the friends and relatives of passengers on board Malaysia Airlines Flight 17, which fell from the sky on Thursday over Ukraine.
The international health community is also reeling from the loss of a number of their colleagues, including a revered AIDS researcher, who are believed to be amongst the passengers on the tragic flight.
The victims were on their way to the International AIDS Conference that is scheduled to begin this weekend in Melbourne, Australia. They were flying from the Netherlands to Australia, via Kuala Lumpur.
One of the victims is prominent Dutch scientist Joep Lange, a pioneer in HIV research and a former president of the International AIDS Society, which organizes the conference. His partner Jacqueline van Tongeren was also on the flight with him, says the Health[e] Foundation, co-founded by Lange.
"He was a real hardcore scientist, but on the other hand, he really had the heart of an activist. He was quite bold and a little bit of a troublemaker," said Albert Wu, professor at Johns Hopkins Bloomberg School of Public Health. Wu had helped Lange plan the 1991 AIDS conference.
"(Lange) was one of the first people to advocate spreading HIV medications to Africa," says Wu. At the time, the medication wasn't being delivered because of refrigeration problems.
"He said, 'If Coca-Cola can deliver cold beverages to Africa, why can't we deliver HIV medication?' And he helped make it happen," recalls Wu.
The Malaysia Airlines passenger jet crashed in a rebel-controlled part of eastern Ukraine on Thursday, spurring swift accusations from Ukrainian officials that "terrorists" shot down the aircraft. Ukrainian security services have released a recording of an intercepted telephone conversation between soldiers that Ukraine says proves rebels are to blame.
The U.S. has concluded a missile shot down the plane, but hasn't pinpointed who was responsible, a senior U.S. official told CNN's Barbara Starr.
The identities of the 298 passengers on board MH17 have not been released by the airline. Meanwhile, friends and family of passengers have expressed grief and shock through social media, amongst them are people who knew attendees of the AIDS conference.
The World Health Organization was also able to confirm to CNN that their employee Glenneth Thomas was on board and heading to the International AIDS Conference.
Thomas' friend Gina Manola told CNN that he was "a brave, curious person, adventurous. And a lot of people I think were drawn to him. He was a really wonderful person doing great work in the world," adding that he was planning his 50th birthday celebration.
Malaysia Airlines was able to give a breakdown of the known nationalities of the passengers: At least 173 were Dutch, 28 were Australians, 28 were Malaysians, 12 were Indonesian, nine were from the United Kingdom, four were from Germany; four were from Belgium, three were from the Philippines, one was Canadian and one was from Hong Kong.
Authorities are still trying to determine the nationalities of the other passengers.
At least one passenger was from Hong Kong, the city's Immigration Department confirmed with local media on Friday afternoon.
'I wait for you'
The 15 crew members on board were all Malaysian nationals, officials said. One of them was Shazana Salleh -- her best friend, Carmen Low Kar Marn recalls driving to the airport before the flight.
"I just sent (Salleh) to the airport and then I just said 'I wait for you to come back' and (she) never come back," Low told CNN's Anderson Cooper.
When asked if the loss of her best friend seemed real to her, Low replied through tears: "I just hope it is a false. I try to message her, but no answer."
Other travelers who were fortunate enough to miss the tragic flight are still in shock.
"I'm shaking ... I didn't know what to do ... I'm feeling physically sick," says a woman carrying her baby at Amsterdam's Schiphol Airport. She was supposed to be on MH17 but had just missed it.
"I was coming to the airport in a taxi, just crying, I feel that I have been given a second chance."
Thursday's crash marks the second time this year that Malaysia Airlines has faced an incident involving a downed plane.
On March 8, Malaysia Airlines Flight 370 disappeared. That Boeing 777 had 239 people on board. Searchers have found no trace of MH370 or its passengers, despite extensive search efforts.
Sarah Bajc, whose partner of two years was a passenger on MH370, said the latest incident brought back memories of the earlier tragedy.
"At first I thought it might just be a joke, you know, something going through Twitter because that's how I found out about it. All the wounds just opened right back up again. I'm so sorry for all those families," Bajc told CNN.
"We still don't know what happened to MH370. It's not
an acceptable situation that we haven't fixed that problem yet and now we have a whole new one to deal with."