In a tweet, the Orlando Police Department identified the suspect as Kevin James Loibl, releasing a headshot and saying that he was 27 and from St. Petersburg, Florida.
Authorities yesterday said they believed he travelled from elsewhere in Florida to Orlando, where Grimmie had given a concert, intent on targeting her.
Grimmie, 22, performed late Friday with the group "Before You Exit" at Orlando's Plaza Live Theatre and stayed on to sign autographs and sell merchandise.
Grimmie was rushed to the Orlando Regional Medical Center, but died of her injuries.
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In addition to two handguns and a hunting knife, the shooter was also carrying two loaded gun magazines, police said.
"The suspect travelled to Orlando, apparently, to commit this crime, and then had plans to travel back to where he came from," Police Chief John Mina told reporters.
Detectives are scrutinizing the suspect's cell phone and computer as they search for a possible motive.
Unarmed security guards at the concert conducted bag checks, police said, but failed to discover the shooter's weapons.
Most people at the event were "young kids," which "isn't a crowd that you would suspect would be carrying guns," he added.
About 120 fans were still milling around the theatre when the shooting occurred, Mina said.
Authorities said they were trying to determine if the shooter knew Grimmie or was a deranged fan.
The shooting likely adds fuel to the long simmering debate over gun control in the United States, where such weapons were used in more than 11,200 murders in 2013, according to the Centers for Disease Control and Prevention.