Updates From WFTV
Shooter has been identified.
It also includes the answer to ScullyO's question about security. There was security patrolling the venue, but none were armed. So far I haven't read anything that indicates whether any were with Christina, especially since her brother was the one to tackle the assailant before he shot himself.
The article also mentions he may have planned to return home after that, so the suicide may have been unplanned? Did he really think he would be able to walk away from that?
In addition, I saw some other articles reporting the shooter was not unknown to the Grimmie family, but this one says there's no indication of Christina having known the shooter.