2:56 PM PT -- Wendell Pierce just shared a touching tribute to his friend and former co-star, saying ... "The depth of my love for this brother, can only be matched by the depth of my pain learning of his loss."
Pierce calls Williams an "immensely talented man with the ability to give voice to the human condition portraying the lives of those whose humanity is seldom elevated until he sings their truth." He says Williams was "Always truthful, never inauthentic. The kindest of persons."
"The Wire" star -- who played Det. Bunk Moreland -- also reminisces about their time together on the show, and their famous park bench scene in which Pierce says they "aimed to take that moment in time together and say something about Black men."
Pierce concludes ... "So to you, my brother Mike, there is a small comfort that I know, you knew how much we loved you.
Michael K. Williams -- best known for his breakout role as Omar Little on "The Wire" -- is dead from a suspected drug overdose ... TMZ has learned.
According to law enforcement sources ... Williams was found dead in his Brooklyn apartment Monday after a relative hadn't heard from him in a couple days and went to check on him.
We're told the actor was found in the living room of his home, and drug paraphernalia was on a table nearby ... suggesting he may have died from an OD. NY Post first reported the death.
After years of minor roles on TV and movies, Williams became a household name as Omar -- the gritty, streetwise and homosexual criminal on HBO's "The Wire" ... earning him critical acclaim and adoration from fans.
Williams would go on to star in several other hit HBO series' -- like "Boardwalk Empire," "The Night Of" and more recently "Lovecraft Country" -- as well as movies like "12 Years a Slave" and "Assassin's Creed."
One of the actor's trademarks was his signature facial scar -- the result of a bar fight he got involved in on his 25th birthday that almost killed him. According to Williams ... the scar helped to launch his acting career, leading to calls to do music videos and some minor work playing a thug in TV shows.
Williams was a 5-time Emmy nominee, and when we last saw him we had a good convo about his nom for 'Lovecraft.'