The Maroon 5 frontman mentored the 22-year-old on Season Six of the hit singing show in 2014, helping her reach the final and finish in third place.
But following her tragic death in Orlando, Florida, after 27-year-old gunman Kevin James Loibl opened fire during a fan meet and greet, Adam was quick to pay his respects to the talented singer.
"(My wife) Behati (Prinsloo) and I are absolutely devastated and heartbroken by Christina Grimmie’s tragic death," he began in a statement posted on his official Facebook page. "Our hearts go out to her family. Christina was a natural, a gifted talent that comes along so rarely. She was taken from us too soon. This is yet another senseless act of extreme violence. I am left stunned and confused how these things can conceivably continue to happen in our world.”
Christina was signing autographs near a merchandise table after her concert at the Plaza Live Theater with rock band Before You Exit when Loibl, armed with two guns walked up and shot her, before shooting himself as the star's brother Mark tackled him, and was pronounced dead at the scene.
Christina was rushed to the Orlando Regional Medical Center, where she was later pronounced dead.
"It is with a heavy heart that we can confirm that Christina has passed and went home to be with the Lord. She was shot at her show in Orlando, and unfortunately didn't survive the gun shot wounds," her representative told People.com.
"We ask at this time that you respect the privacy of her family and friends in their time of mourning."
Fellow The Voice judges have also paid tribute to the young singer, with Christina Aguilera and Blake Shelton also taking to social media to share their shock and sorry.
"So sad passing of @TheRealGrimmie. Beautiful member of #TheVoice family & true #Fighter. My heart goes out to her family, friends & fans. xo," Christina, 35, wrote on Twitter, while Blake, 39, wrote: "I'm stunned and disgusted and heartbroken that we lost that sweet little girl... Keeping @TheRealGrimmie family in my heart and mind."
James MCVey from British band The Vamps, also posted a selfie with Christina on Twitter and wrote "she was incredible" in the caption, and he later explained to WENN that he and bandmate Connor Ball had been watching her YouTube.com videos for six years and had met through mutual music friends.
"We hung out a few times actually," he said at the Capital FM Summertime Ball with Vodafone. "My friend text me saying 'have you seen what’s happened?' I thought it was like, not real. It’s horrible, it’s quite shocking, me and Connor were big fans of hers. (It's) really, really sad."
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