Darren Criss is mourning the loss of Glee costar Cory Monteith. Two days after learning of Monteith's tragic death, the 26-year-old actor attended a screening of his new movie, Girl Most Likely, at Landmark Sunshine Cinema in New York City on Monday, July 15.

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As a tribute to Monteith, Criss wore a black ribbon on the collar of his gray suit, which can symbolize remembrance or mourning. An attendee tells Us Weekly that Criss "looked rather sad and somber" during the event. "He only smiled when he as posing for photos and obviously wanted to get off the carpet as soon as possible," the insider says.

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Though Criss did attend the screening, the singer canceled has canceled his July 16 appearance on Live with Kelly & Michael. Glee costar Matthew Morrison also has canceled his performance on the show scheduled for July 18. 

A source previously told Us that Morrison, 34, dedicated a song to Monteith during his encore engagement of Up Close and Personal with Matthew Morrison at 54 Below in NYC on July 14. Before the show started, the insider tells Morrison told the crowd, "'We lost a great young man too soon.' He said Cory was a beautiful person."

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Monteith was found dead in his Vancouver hotel on July 13 at the age of 31. The British Columbia Corner's office told Us they "might" have an update on his cause of death on July 16, but that "final cause of death might be several days or even a couple of weeks after that."

This article originally appeared on Usmagazine.com: Darren Criss Wears Black Ribbon, Looks Somber at Movie Premiere After Cory Monteith's Death