22-year-old Grimmie was signing autographs near a merchandise table after her concert at the Plaza Live Theater in Orlando on Friday (10Jun16) when she was approached by 27-year-old gunman Kevin James Loibl.

Loibl, who was armed with two guns, shot Christina before shooting himself as the star's brother Mark tackled him to the ground. The singer was rushed to the Orlando Regional Medical Center, where she was later pronounced dead.

Selena Gomez, whose stepfather Brian Teefey managed Christina, took to social media on Saturday (11Jun16) to pay her respects. The singer shared a black and white photo of her with The Voice star on Instagram, and wrote alongside it, "My heart is absolutely broken. I miss you Christina."

Teefey, who discovered the star on YouTube, echoed his stepdaughter's sentiments in a statement on Saturday. "Words cannot begin to describe the pain I am feeling," he told People.com. "I learned this business through the eyes of a father and Christina was like a second daughter to me."

He has set up a Go Fund Me page to support the singer's family, which as of Sunday (12Jun16) stands at more than $70,000 (£43,750).

Christina's brother Mark, who was hailed a hero for his efforts in tackling the gunman to the ground, wrote a touching tribute to his sister on Facebook in the wake of her shocking death.

Sharing five photos of his sibling on Facebook, he asked others to join him in celebrating her life. "I would love all and any of you to post pics of you and her and/or memories you have of her down in the comments," he wrote in the post on Saturday. "I will cherish it forever and always. So please do that for me."

Mark said his little sister was a superstar, and confessed he did not know what he would do now that she was gone. "Christina was more than my sister," he wrote. "She was a partner in life. A superstar. A goofball. Introverted. And a friend to everyone. Genuinely.

"But above all... she was my baby sister. She loved the Lord and her family and was always there for me and I honestly don't know what ill (sic) do without her."

At a press conference on Saturday morning, Orlando police chief John Mina said the investigation was ongoing into the motive behind Loibl's attack. He also praised Mark for his efforts in tackling the armed gunman, and added, "Very heroic actions by Marcus to jump in, and definitely could have prevented further loss of life."

The Voice host Carson Daly shared his shock over the death of Christina on Saturday, and revealed he was surprised she didn't win the talent show when she came third on the sixth season.

"I just think we're all still in shock," he told NBC's Today Show. "We're just so saddened by the news of Christina, who is such an incredible talent and incredible person. It still seems so fresh... I mean it's just, it's just so sad, so young.

"She was special. I mean, she really was special. She would walk in a room and she had an infectious laugh.She was determined, she was confident but she was so incredibly sweet. You would never forget meeting her. I'm shocked she didn't actually win season six."

The Grimmie family faced further heartache on Saturday as it was revealed the star's Twitter account was hacked shortly after her death. Fans were quick to call out the morbid message that simply said, "The end."

However, it has since been confirmed the message did not come from an official source and it has now been deleted, Digital Spy reports. The singer's Twitter page has now been updated, with the header and profile pictures paying tribute to the star.