A man opened fire on her when she was signing autographs after a concert in Orlando. The 22-year-old singer died in a local hospital.
The assailant - who was tackled by Grimmie's brother - then shot and killed himself, reported E! online.
In 2014, Grimmie finished third during season six of "The Voice."
In a tweet, Orlando's police wrote: "With deep regret, we have confirmed Christina Grimmie, @TheRealGrimmie has died from her injuries."
Meanwhile, Grimmie's publicist said: "It is with a heavy heart that we can confirm that Christina has passed and went home to be with the Lord."
Grimmie first came to prominence as a teenager for her renditions of hit songs, amassing a huge following on Youtube.
In 2011, she released her debut musical recording "Find Me." Her second EP - Side A - followed in February 2016.