The 22-year-old singer had performed with the band Before You Exit at The Plaza Live in Orlando. The concert ended around 10pm and Grimmie was shot as she signed autographs for fans at a merchandise table.
Grimmie’s brother immediately tackled the gunman who then shot and killed himself during the struggle, police said.
The gunman was not identified, and Orlando police have not said why he attacked the singer. An investigation is ongoing.
Grimmie, who was born in New Jersey, finished third during season six of the US series of The Voice, competing on the team of Maroon 5 star Adam Levine.
Before Friday night’s concert the singer posted a now hugely poignant message to her more than 700,000 Twitter followers imploring them to come to her gig.