By Joseph Ax

(Reuters) - Christina Grimmie, a rising singing star who gained fame as a YouTube sensation and contestant on television's "The Voice," died after being shot while signing autographs at a concert hall in Orlando, police said on Saturday.

The suspected attacker, identified as 27-year-old Kevin James Loibl of St. Petersburg, Florida, died of a self-inflicted gunshot wound after he was tackled by the 22-year-old singer's brother, police said.

Authorities believe the suspect traveled to Orlando to carry out the attack Friday evening. They said he had two loaded handguns, additional ammunition and a hunting knife at the time of the shooting.

Orlando Police Chief John Mina told reporters the suspect did not appear to have a criminal record and there was no indication he and Grimmie knew each other. Mina said it appeared he may have been a deranged fan.

"That'd be speculation, but that's what it's looking like. We believe he came here to commit this crime," Mina said when asked about that possibility.

Detectives will search the suspect's home, cell phone and computer before releasing further information, he added.

Grimmie was signing autographs for fans inside the Plaza Live concert hall at the time of the shooting, around 10:30 p.m. (0230 GMT on Saturday). She had just appeared as the opening act for the band Before You Exit.

The suspect approached Grimmie and opened fire. He was then rushed by the singer's brother.

"Her brother, Marcus, is a hero and possibly saved countless other lives. He is not injured," Orlando police said in a statement, adding there were about 120 people at the venue at the time.

Her brother mourned the loss of his sister in a Facebook post on Saturday.

"Christina was more than my sister," People magazine reported the post as saying.

"She was a partner in life. A superstar. A goofball. Introverted. And a friend to everyone. Genuinely. But above all ... she was my baby sister. I honestly don't know what I'll do without her," he wrote in the post.

Christina Grimmie was taken to a local hospital in critical condition and died early Saturday morning. The suspect died at the scene of the shooting.

Although patrons had their bags and purses checked for weapons at the venue, there were no metal detectors and the security guards were unarmed, Mina said.

'BEAUTIFUL SOUL'

The attack, the latest high-profile shooting to rock the country, drew a quick response from anti-gun activists.

"While the details of this shooting are still being investigated, one thing we already know is that there is so much more Florida policymakers can do to prevent gun violence and keep guns out of dangerous hands," said Dan Gross, the president of the Brady Campaign to Prevent Gun Violence.

A New Jersey native, Grimmie first gained attention several years ago for her YouTube videos featuring covers of pop songs, which drew millions of views. In 2014, she placed third on the "The Voice," a singing competition broadcast on NBC.

Fans took to social media to express their sorrow, with the hashtag #RIPChristina trending on Twitter.

"There are no words," tweeted "The Voice" early on Saturday. "We lost a beautiful soul with an amazing voice."

Josh Kaufman, who beat out Grimmie to win the 2014 season of "The Voice," tweeted, "My deepest and most sincere condolences go out to the family of @TheRealGrimmie. Such a tragic loss."

Grimmie's own Twitter account still showed a video she posted on Friday asking fans to come out to see her perform. Her account tweeted a simple message Saturday morning: "The end." The post was retweeted more than 65,000 times within an hour.

Her killing was reminiscent of the 1995 fatal shooting of Selena Quintanilla-Perez, a 23-year-old singer best known as Selena. Already an established star, Selena was gunned down in a Texas motel by the founder of her fan club.

Last month, Japanese pop star Mayu Tomita, 20, was repeatedly stabbed during a fan event at a Tokyo train station but survived the attack. Police charged a 27-year-old man with attempted murder.

(Additional reporting by Brendan O'Brien in Milwaukee; Editing by Paul Simao and Steve Orlofsky)