Police say 39-year-old Errol Hillary open fired on a crowd at "The Mansion" in Mount Vernon.
One of the security guards tackled Hillary and held him until police arrived.
He described the moment he stepped into action.
I was actually standing right in front of him when he started shooting," the security guard said, "I said, 'You know what, I got to jump on him.' So I jumped on him, you know to try to stop him from shooting anyone else."
The shooting killed the club's owner O'Neal Bandoo.
Eyewitness News spoke to his mother at an anti-gun violence event near the scene.
She said Bandoo's death has been hardest on his six children.