Police responded to the incident at around 7:30 p.m., delaying the start of the show for more than an hour.
The lockdown caused a major traffic backup on I-880 and on the foot bridge from the Coliseum BART station, as hundreds of concert-goers arrived to see the legendary composer perform.
"Got here in line and right when we got to the front gate, they shut the gate on us and told us that there was a security situation they needed to handle before they would open it," said Brett Strommen who was one of the attendees waiting outside.
People already inside the show were forced to wait while the investigation unfolded.
Some told us it wasn't made clear to them what was going on.
The gates were reopened at around 9 p.m.
We've reached out to Oakland police - they did not confirm what caused the delay and lockdown.
We also reached out to Oakland Arena, but did not hear back.