Horrifying footage shows when a 17-year-old gunman opening fire during a Halloween celebration in downtown Orlando that left two dead — and the moment a heroic police officer tackled the shooter.

Video released by the Orlando Police Department Friday allegedly shows Jaylen Dwayne Edgar walking through the crowd in a yellow shirt and backpack before he starts shooting, sending costumed revelers running for their lives.

Edgar attempts to flee the scene but a police officer who saw him pull the trigger immediately tackles him to the ground by himself before three other cops pounce on him.

“Get on the ground!” the cop yells at the teenager repeatedly amid the chaos, bodycam footage from the arresting officer shows.

The shooter says “It’s not me” but he’s quickly taken into custody.

At least two people were killed and six others were wounded in the mass shooting, police said.