The actor who plays Tom Haverford on the NBC comedy wrote an emotional tribute on Friday for Wittels on his Tumblr.
"There are so few people that you meet in life that give you that feeling that you've found a real unique, original person," he began. "Harris Wittels was one of those and we lost him yesterday."
He then expressed his shock, "I'm still waiting for the other phone call to let me know that Harris is okay and this was all a horrible misunderstanding. I don't know when my brain is going to be able to process the terrible feeling that fills my heart with dread and my eyes with tears every 20 seconds when I realize this very special person is really gone."
Ansari continued his post by sharing stories and what he loved about the producer. "Harris was truly a sweet guy. He was so lovable even when saying the most disgusting things.You just couldn't help but love him," he added. "He had the most ridiculous opinions on everything from food to dating to music and he’d defend them to no end. He loved to make ridiculous boast that he insisted he could achieve."
TMZ reported that drug paraphernalia was found in Wittels' home and that his death came after an apparent overdose.
Ansari addressed Wittels' struggle, "We knew Harris had issues with addiction but things were pointing in the right direction. He was getting treatment and focused on his career and the opportunities ahead."
A friend of Wittels told ET that he was reportedly depressed following Parks and Recreation's production wrap and that he was having trouble finding work.
Ansari ended his tribute with a touching message about how he hopes people will remember Wittels, "I hope people reading this realize what a incredibly unique man you were, and what brutal a loss it is for those who knew you and also for those who never had the pleasure," he wrote. "This has been so hard to write because I just keep wanting to add more and more stories and more jokes and more everything, but I’d never be able to finish it. You are far too special to sum up in any kind of piece like this. You were one of the best and we all will miss you."
To read Ansari's full tribute, click here.