It is unclear what motivated gunman Kevin James Loibl to kill Christina Grimmie, police say.
Christina Grimmie, 22, was shot while signing autographs after a concert in Orlando, Florida, on June 10, and died in hospital.
Orlando police chief John Mina said the gunman, 26-year-old Kevin James Loibl, came from the city of St Petersburg in Florida to confront the singer.
John Mina said Kevin James Loibl did not seem to know her personally but speculated that he may have been a deranged fan.
After a struggle with Christina Grimmie’s brother, Kevin James Loibl shot himself dead.
Christina Grimmie first came to prominence as a teenager for her renditions of hit songs, amassing a huge following on YouTube.
In 2014, she was a contestant on The Voice.
Police say Christina Grimmie was shot about 22:45 local time on June 10 at The Plaza Live in Orlando.
John Mina said: “She was doing a meet-and-greet, just signing autographs and selling merchandise.
“This white male approached her and opened fire, striking her.”
The police chief praised Christina Grimmie’s brother Marcus for his “very heroic” actions in tackling the gunman, who he said was carrying two handguns and a hunting knife.
“It definitely could have prevented further loss of life,” John Mina said.
Other people have been issuing messages of support for Marcus Grimmie, including a survivor of the 2012 Sandy Hook elementary school shooting in Connecticut.
Ashley Cech, who campaigns against gun violence, wrote an open letter to Marcus Grimmie.
She wrote: “Today the world was reminded that there is no love quite like that between an older brother and his little sister.”
Christina Grimmie had been performing with the band Before You Exit.
Up to 100 people were at the concert, but only a handful remained at the venue when the shooting happened, officials said.
John Mina said unarmed security guards had checked bags as people entered the venue, but no metal detectors were used and no body searches were made.
News of the attack spread quickly on social media, with many fans voicing their shock and anger.
When the first reports of the shooting surfaced, #PrayForChristina was the top trending hashtag on Twitter.
The hashtag changed to #RIPChristina after Christina Grimmie’s death was confirmed.