They had a bromance before we even had the word. And tributes like this are the reason why.
"First off I am so sorry I am not there with you today," Feldman writes. "By that I mean my physical body is not with your physical body. However you know that my heart is right at your side."
Feldman tells Haim that the reason he opted not to go to the 200-strong private service was "out of respect" for his family, particularly his mother, who wanted "to minimize the media attention as much as possible."
We're guessing releasing an open letter to your deceased friend online may not exactly grant him solitude, but the intention is definitely there.
"I miss you so much already," Feldman continues, hinting that Haim's passing wasn't exactly unexpected. "When I think of something funny I don't know who to tell it to. I find myself trying to call you but then remember your not there. I think about the new movies we will soon be doing together and then suddenly realize that the dream is over.
"I always feared this day would come, and often rehearsed how to face it. But once confronted with the reality of it, it's so much more painful than I could have ever imagined."
As for why, well, no one understood Feldman quite like his troubled BFF.
"Nobody will ever understand the brotherhood we shared. Nobody will ever get the inside jokes we told. Nobody will understand the magic of 22/222. Nobody will ever know how to do the secret Corey handshake. Nobody will ever make me laugh as hard as you did. Nobody will ever make me fight as hard as you did. Nobody will ever challenge me the way you did. Nobody will ever need me the way you did."
In fact, Feldman claims that his "mission in life became saving" Haim's.
"In a dark and lonely world with spiteful angry people we always understood each others pain."
Feldman tells his pal how "hounded" and "barraged" he has been by the media in the wake of Haim's surprise death last week, and laments that he was "not been given my own time" to grieve.
Of course, Feldman bears some of the responsibility for that, as he voluntarily appeared on Larry King Live last week. Still, he defended the decision by saying he went on "to be strong to send a message."
"I never knew your death would have such a huge impact on the world," he writes. "I only wish you could see the way the world is mourning over your absence. I wish you could see how big the story is.
"It is such a shame they all had to wait until you were gone to give you the respect you were due as an actor which is what you truly were."
Feldman also hints at things to come in his letter, as he is among those organizing a memorial for Haim to take place in Los Angeles.
"I will do my very best to give you a memorial that is a celebration of your life the way you would have wanted it...with everybody laughing and rocking out!
"My heart is so broken and I know there are so many who feel the same way I do. We will remember your spirit and your fans will help me keep your legacy alive. I pray that you are safe and warm and finally filled with peace."
(Originally published March 17, 2010, at 7:16 a.m. PT)
Pay tribute to the actor with a look through our Remembering Corey Haim gallery.