The shooter who initiated the gun battle was shot dead, according to authorities.
In the YouTube clip, which the poster, Nicholas Gramenos, claims was captured outside a Las Vegas courthouse, more than 45 gunshots can be heard. The camera is too far from the building to see the battle.
"Shooting outside of a Las Vegas courthouse," Gramenos says. "Hell of a morning for jury duty."
The multi-story building where the shooting occurred houses federal courts and offices for federal officials including U.S. Sens. Harry Reid and John Ensign.
A hospital official said one court officer has died after being wounded in the shooting and a second officer is in serious condition.
The U.S. Marshals Service says the victims included a deputy U.S. marshal and a court security officer. It was not immediately known which of the officers died. Rick Plummer of University Medical Center in Las Vegas says the dead officer was 65 years old.
"A Deputy U.S. Marshal and Court Security Officer were shot at the Lloyd D. George Federal Courthouse in Las Vegas this morning," U.S. Marshals spokesman Jeff Carter said Monday. "The gunman was shot by Marshals Service personnel and has been pronounced dead. The Deputy U.S. Marshal is in stable condition at a local hospital. Unfortunately, the Court Security Officer succumbed to his wounds and passed away. We are not releasing any names until next-of-kin notifications are complete. The courthouse is still being secured. We do not know the motive for the shooting at this time and the investigation into the shooting is still underway. I will provide more information as it becomes available."
FBI Special Agent Joseph Dickey said the gunman died soon after the shootout that happened around 8 a.m.
Police and federal agents swarmed the multi-story building, and paramedics wheeled at least two people out and down a ramp to ambulances. There was no immediate word on the identity of the shooter.
Las Vegas police spokeswoman Barbara Morgan said the shooter had been shot in the head.
"It looks like he went in there and just started unloading, we don't know," Morgan said.