“If you knew him – you loved him. A brilliant actor and even better person,” Mr Liebman wrote.
“May his memory forever be a blessing. Our hearts are so broken. He will be very, very missed.”
In statements to Hollywood news outlets, he added that Whitlock passed away in New York after a short illness.
On The Wire, Whitlock played a corrupt politician, and was known for his profane catchphrase, which Whitlock himself had developed.
The phrase was based off his uncle, he said in a 2008 interview, and he had also said it in the same intonation in other films before debuting on HBO’s The Wire.
He was recognised throughout his career for his elongated version of a common curse word.
“I was in, I think, Grand Central Station and far away I heard someone say it and they’d be kind of smiling” he said in the interview. “I’m glad people enjoy it.”
On Veep, he played a comical version of the US secretary of defense, who runs for office against the main character, played by Julia Louis-Dreyfus.
Whitlock featured in six films by Spike Lee, including 25th Hour, She Hate Me, Red Hook Summer, Chi-Raq , BlacKkKlansman and Da 5 Bloods.
The native of South Bend, Indiana, also had roles in films Pieces of April, Enchanted and Cars 3 and Lightyear, as well as TV roles in the Law and Order franchise.