at his new year's eve party in san francisco, dustin diaz took these photos of his friend. they walked to watch the midnight fireworks. he snapped a photo and posted it before leaving in a car. diaz said he was happy. there was no hint of the emotional issues the private investigator says he had. >> we were having an awesome time. we were laughing. a lot of the photos are of him laughing. >> he had a past history of unstableness and it had to deal with emotional, you know, outburst. never physically harmed anyone, but he talked about, you know, issues where he would be better off not being around. >> a programmer at yahoo! is so valuable, the company hired the private investigator to find him. the investigator would not confirm this. he made it home, but left his diabetes kit, medication, and kitten behind. on new year's day, he tweeted a friend, thanks for being a great friend. apparently, he has taken off to thailand before without telling anyone. it's a mystery this time. he has tattoos and a sacred heart with cross bones on his chest. kpix5. >> a woman is in the san fra

at his new year's eve party in san francisco, dustin diaz took these photos of 28-year-old friend.lked to watch the mid nielth fireworks on the embarcadero. he snapped a photo and posted it on instagram before leaving in an uber car. he was happy. there was no hint of the emotional issues a private investigator said he had. >> we were having like an awesome time. we were laughing. a lot of the photos are of him just laughing. >> he had a past history of unstableness, and it had to do with emotional, you know, outbursts. never physically harmed anyone, but he talked about, you know, issues where he just, you know, would be better off not being around. >> friends say a programmer at yahoo is so valuable the company hired a private investigator to find him. the investigator would not confirm this. he says he made it home but left his diabetes kit, antidepressant medication and kitten behind. on new year's day, he tweeted a friend, "thanks for being a great friend." apparently he's taken off to thailand before alone. it's mystery this time. he has tattoos of linux code and a sacred hea

. >> reporter: at his new year's eve party in san francisco, dustin diaz took photos of the 28-year-old friend luke ar dui ni. they went to watch the midnight fireworks on the embarcadero. a picture was posted on instra gram before leaving in an uber car. he was happy and no emotional issues. >> we are having like an awesome time, laughing. a lot of the photos of him just laughing. >> he had a past history of unstableness and had to do with emotional, you know, outbursts. never physically harmed anyone. but he talked about, you know, issues where he just, you know, would be better off not being around. >> reporter: friends say arduini an employee at yahoo is so valuable the company hired a private investigatory find him. the investigator wouldn't confirm it. he said the manmade it home but left his diabetes kit, antidepressant medication and kitten behind. on new year's day, he tweeted a friend, thanks for being a great friend. apparently, the man has taken off to thailand before alone. it's a mystery this time. he has tatoos of linux code and the sacred heart with crossbones on his che