Christina Grimmie's brother Marcus mourns 'superstar' baby sister's death

Christina Grimmie's brother Marcus Grimmie has paid a touching tribute to his "baby sister" after she was shot dead in a concert in Florida on June 10.

Marcus took to his Facebook account to express his grief and said that Christina was more than a sister to him, adding she was a "superstar" and a "friend to all," reports E! Online.

He further said, "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 I'll do without her."

Marcus also thanked for the scores prayers and other messages of support, which are pouring in on social media.

Reportedly, Christina was extremely close to her father and mother, who has been battling cancer, and shared an endearing bond with that her brother. He often performed with Christina and helped her out with her YouTube videos. The duo even had 'Player 1' and 'Player 2' tattooed on their arms.

Marcus, who tried to take on the gunman as he opened firing during the concert, is largely hailed as "hero" for doing so.

While the motive for the shooting remains unclear, the police are still investigating the incident.