The gunman who shot and killed singer Christina Grimmie travelled to her Florida gig specifically to attack her, police said.
Kevin Loibl was carrying two handguns, two loaded magazines and a hunting knife, when he entered The Plaza Live concert venue in Orlando.
Grimmie, who rose to fame after appearing on the US version of The Voice, was signing autographs after her performance when Loibl opened fire.
Grimmie's brother, Marcus, immediately tackled the gunman, who then shot and killed himself during the struggle. The 22-year-old singer was taken to hospital after the attack on Friday night, and died early on Saturday.
Orlando Police Chief John Mina said Loibl, 27, of St Petersburg, Florida, did not appear to know Grimmie personally.
He said: "She was doing a meet-and-greet, just signing autographs and selling merchandise. This white male approached her and opened fire, striking her.
"We believe he came here to commit this crime."
Grimmie, from New Jersey finished third during season six of NBC's The Voice in 2014, competing on the team of Maroon 5 star Adam Levine.
She began amassing a following on YouTube as a teenager, gripping online viewers with her powerful renditions of hit songs. Her videos on YouTube have notched up millions of views.
Earlier, police said Grimmie had performed with the band Before You Exit at the gig, which ended around 10pm local time, and she was shot as she signed autographs for fans at a merchandise table.
Marcus Grimmie's actions in bravely tackling Loibl stopped the gunman from hurting others, police said. Around 120 people were in The Plaza Live at the time.
"Very heroic actions by Marcus Grimmie to jump in and it definitely could have prevented further loss of life," Mr Mina said.
Detectives were searching Loibl's mobile phone and social media accounts looking for clues as to a motive, the police chief said, but they were not aware of any history of him stalking Grimmie.
At Loibl's home in St Petersburg, someone had left a note on the front door, expressing the "deepest sorrow" for the loss "to the family, friends & fans of the very talented, loving Christina Grimmie".
The note said there would be no other comment. No-one answered the door to the one-storey house that had a rusted, metal animal trap in the yard.
Loibl had made travel arrangements to come to Orlando alone, as well as to go back home, but he did not have a car, Mr Mina said.
There were unarmed security guards at The Plaza Live and they checked bags and handbags for contraband, but there were no metal detectors or pat-downs of people as they entered, Mr Mina said.
A spokeswoman said all events at the venue had been suspended until further notice.
After the concert, 17-year-old Kaitlin Martin was standing with a group of other fans outside The Plaza Live, waiting for members of Before You Exit to come out, when she heard several loud "pops".
She said: "We thought at first they were balloons ... but then security started running all over the place yelling at people to get out because someone has a gun and someone is shooting.
"Everyone is just running all over the place," said the teenager, who travelled to the concert from Brunswick, Georgia. "It was chaos."
Grimmie had posted a video of herself shortly before the concert was scheduled to begin, encouraging fans to come and see her perform.
The Voice paid tribute to Grimmie on its official Twitter page: "There are no words. We lost a beautiful soul with an amazing voice."