A man has been killed in a shooting at a weigh-in for a World Boxing Organization (WBO) title fight in the Republic of Ireland.
Two other men were injured in the incident at Dublin's Regency Hotel at about 14:30 local time on Friday.
It is understood the gunmen were dressed as police officers and armed with AK47 assault rifles.
Police investigating the suspected gangland crime have sealed off the hotel for a forensic examination.
On Friday evening, Irish police held a press conference in Dublin.
Ch Supt Barry O'Brien said three men were shot in the attack and all were taken to hospital where one of them, a man in his 30s, subsequently died.
"Gardaí (Irish police) believe that at least four people were involved in the incident," he said.
"Two were described at wearing police style uniforms similar to a SWAT team uniform, including metal helmets.
"The men were armed with automatic weapons. Two others were carrying hand guns.
"One was a man disguised as a woman and wearing an auburn wig and the other was stocky and wearing a beige cap."
Police said a full investigation was under way and appealed for anyone who was at the hotel to contact police.
The event was ahead of Saturday night's European lightweight bout between Jamie Kavanagh and Antonio Joao Bento.
Kavanagh tweeted to say he was "OK", adding: "I was lucky today is all I can say."
BBC Radio Foyle's sports reporter Kevin McAnena, who was at the weigh-in, said he "never felt terror like it" when one of the attackers pointed a gun at him.
He said he saw one of the gunmen shoot a man in the leg "about six feet away" from him.
"I heard two loud gunshots from outside coming into the hotel," he said.
"At which point, two men, who I thought were [police] officers - turns out they were just dressed up in [police] uniform - came in with guns."
He said he believed "the man I saw shot is the man that is now dead".
"That same gunman then looked over at me and pointed the gun at me," he said.
"[Police] have told me since that [the guns] were AK47 rifles.
"It's so surreal, it just happened so quickly, right in front of me.
"A man was shot dead six feet away from me - it's hard to gather your thoughts right now."
The injured men, in their 20s or 30s, have "possible gunshot wounds", police said, and have been taken to hospitals in Dublin.
Mel Cristle, the president of the Boxing Union of Ireland, said the shooting was not indiscriminate and individuals other than the boxers were being targeted.
Speaking to Irish state broadcaster RTÉ, he said people were diving for cover and "they couldn't believe what was going on".
He said there were between 200 and 300 people, including children, at the weigh-in.
The pay-per-view channel Box Nation was due to broadcast Saturday's fight as part of the Clash of the Clans show at Dublin's National Stadium.
But it has said the event has now been cancelled.