- Police say two other men were injured
- The scene has been sealed off, and a technical examination will take place
In a statement, police said authorities were investigating a shooting that occurred at about 2:30 p.m. "at the Regency Hotel, Swords Road, Dublin 9." Authorities said they believe shots were fired inside and outside the weigh-in room, but investigations are continuing.
The BBC showed video, taken by a spectator, of a boxer and others scrambling for safety.
Organizers of Saturday's "Clash of the Clans" at the National Stadium subsequently canceled the boxing event.
The shooting was not an act of terrorism, a police representative told CNN. Investigators are looking into whether it is gang-related.
When emergency workers arrived, they found three injured men. One of the men, described as being in his 30s, was pronounced dead.
Two of the attackers wore helmets and SWAT-style uniforms, police said. They had automatic weapons.
Two others had handguns. One was disguised as a woman with an auburn wig. The second was described as stocky and wearing a beige cap.
The scene was sealed off, and a technical examination of the area was expected to take place. The hotel is popular with tourists.
A burned van was found later.
Police are appealing for anyone who was in the area or may have information to contact them.