Shawn was performing at the Brooklyn Paramount Theatre when he took a moment to tell the crowd that the One Direction star was a "beautiful soul" ... and the shocking news of his death was "devastating."

SM emotionally lamented ... “Liam, we love you. The world is crying for you, brother. And we’re all praying for your son and your family, and I miss you, man. So this one’s for you tonight, Liam, from all of us.”

Shawn then performed his new song "Heart Of Gold" ... which includes the chorus, "You had a heart of gold / You left too soon/It was out of your control / Underneath your skin and bone / You had a heart of gold.”

As TMZ reported ... Liam's sister on Sunday also talked of her love and admiration for the star when shared a heartbreaking note on Instagram ... which included the brutal line, "I'm sorry I couldn't save you."