Gordin, a 28-year-old bank employee, was on vacation in the Egyptian beach resort of Sharm el-Sheikh with his girlfriend, Alexandra Illarionova, when the two friends were having one of their regular online catch-ups Friday.
The two men were extremely close. Since meeting on a vacation in Crimea 10 years ago, they had taken regular vacations together, and Gordin had been best man at Voytolovsky's wedding.
But when Voytolovsky asked his friend over social media how their romantic getaway was going, Gordin was coy on the details.
"He tells me he will tell me everything when he comes here," Voytolovsky told CNN in his St. Petersburg apartment Wednesday.
"I think he did have something to tell me ... I think it was about (getting) engage(d). They wanted to tell us, not in chatting," he says, nodding toward his computer, "but in real life."
The friends never had the conversation. The next day, Gordin and Illarionova boarded Metrojet Flight 9268, bound for their hometown of St. Petersburg, but never made it home.
All 224 people on board, the vast majority of them Russian, were killed when the aircraft crashed in the Sinai Peninsula
It was, says Voytolovsky, "the worst day of my life."
"I still can't believe it."
'Even my grandmother loved him'
Gordin, he says, was a great guy -- an open-minded, kind soul, whose love for animals led him to rescue stray cats. "I am sure you couldn't find a person who could say anything bad about him," he said. "Even my grandmother loved him."
He had met the 28-year-old Illarionova only 10 months ago, but the couple had fallen for each other quickly and moved in together.
Earlier this year, the new couple took a vacation with Voytolovsky and his wife, in an expansion of the vacations the two men had taken for years, in regular escapes from their modest lives in St Petersburg.
The friends had getaways planned for next year -- Hungary, Turkey -- that now won't happen. When Voytolovsky chatted with his friend in Sharm el-Sheikh, he had told Gordin it was a shame he wasn't there with him.
"He was the person who was going to join me for the whole (of) our lives," he says of his friend.
In his grief, Voytolovsky has set up a website to pay tribute to his friend. Featuring photos taken from the couple's social media accounts, it is getting tens of thousands of hits, bringing a small measure of comfort to Voytolovsky. But harrowing times lie ahead.
Voytolovsky says he will travel to Egypt to help Gordin's father identify his body.
"I can't imagine what's going to be there, I know there are not going to be whole bodies," he says, sighing heavily. "There will be some fragments."
It's important to help his friend's family in their time of need, he says.
As for how he will try to deal with the loss, he says he draws a little comfort from the fact that, on the evidence of the photos Gordin and Illarionova posted of their vacation, the couple spent their last days together blissfully happy and deeply in love.
"At least I know the last days of them, they were like in paradise," he says.