Matthew Morrison's emotional tribute to Glee co-star Cory Monteith

The shocking death of Glee star Cory Monteith has saddened the world, and the pain is only worse for those who knew him, including his castmates.

In a performance at the hot-spot cabaret 54 Below in Manhattan's Broadway district, Matthew Morrison--Mr. Shuester, to Glee fans--dedicated the song "What I Did For Love" to Monteith.

According to Us Magazine:

Morrison, 34, chose the tune "What I Did for Love" from the Broadway classic A Chorus Line to dedicate to Monteith and struggled to contain his emotions during the performance. "He was very emotional on stage," the source tells Us. "It was difficult for him to get up to perform, but he did not want to disappoint anyone."

Monteith's girlfriend & costar, Lea Michele, has so far declined to make a statement. The world is respecting her need for privacy, but also keeping her in its thoughts. #PrayforLea is now a trending topic on Twitter.