So the guy in the picture committed suicide in a random hotel room in September 2001. The only thing police knew at the time was the alias he gave to check in to the hotel room, Lyle Stevik. Other than that, no identification at all.
The case remained a mystery despite nation wide searches displaying his body and what they thought he looked like while he was alive. His identity went unknown until 2018, when a group called DNA Doe Project used ancestry DNA to find relatives of his that eventually lead to a positive ID, but the story doesn't end there...
Once they positively identified Stevik, the family requested that his name not be released, so law enforcement and DDP agreed to keep quiet. The decision split the Lyle Stevik community, some were pissed off because they spent up to years of their lives trying to find his identity only to be kept in the dark, and others were satisfied that he finally got a name and didn't care about finding his real name.
This caused several groups on reddit and discord to put the search into their own hands and find out who Lyle Stevik was. And sure enough, they eventually found him, and that is where this photo came from.
That photo is quite rare by the way, the high school Lyle/Christian went to does not have a yearbook public on the internet, they had to track down the year book in real life to get the photo.
Not sure how they found out his identity, my guess is they did the exact same thing the DDP did but with more trial and error.