Gardaí are now tracing the steps of the gunman after the shooting at the club in The Harbour, Bray, Co Wicklow, at around 6.55am yesterday morning.
House to house enquiries, CCTV footage and witness interviews will also prove crucial in the investigation.
“We’re particularly interested in hearing from anyone who was in this area this morning, it is a leisure area and people may have been out walking or walking their dogs. If they saw anything suspicious this morning or in previous mornings or anytime in the last few days please contact us,” said Superintendent Pat Ward from Bray garda station.
This appeal also extended to anyone using the gym who may have seen any suspicious activity lately, or anyone with dashcam cameras who were in and around Bray.
Scene of shooting at Bray Boxing Club (Photo: Kyran O'Brien)
“Hard luck today Katie gutted to see you so upset, you’re a true champ and we're all so proud of you Keep the faith x”
Mr Taylor was rushed to St Vincent's Hospital after the incident and boxer Gary Cully, who has won four professional fights with Pete in his corner, said on his social media page that he was in contact with his coach.
"Just spoke to Pete on the phone, he's doing fine, that's all I know," he posted.
Cully is slated to fight on the Michael Conlan homecoming card at the Odyssey Arena in Belfast on June 30 against an opponent to be confirmed.
Mr Messett is believed to have been shot in the head while Mr Taylor was shot in the arm, with the bullet deflecting into his chest. The other man was hit a number of times in the leg. The two injured men are in hospital, and their injuries are not believed to be life-threatening.
"Gardaí can confirm that one man aged 50 years has died following a shooting incident in Bray, Co. Wicklow this morning," a garda spokesman said.
"The body of the deceased remains at the scene pending the arrival of the State Pathologist and a technical examination of the area is being carried out by Garda Crime Scene Examiners.
"Two other men, aged 35 and 57, who were injured in the incident have been taken to hospital."
Gardaí pictured on the pier following a shooting in Bray Boxing Club (Photo: Mark Condren)
The boxing club is where Ireland's Olympic, European and World champion Katie Taylor previously trained. It is understood she is now training in the US as she continues her professional career. The club was set up by her father and was also home to former Irish champion Adam Nolan.
The €300,000 state-of-the-art facility was officially opened in February 2014.
Early reports suggest that the deceased man opened the door to the gunman before being shot. Gardai are investigating whether the gunman then entered the building before shooting the other two men, and then making his escape.
Anyone with information is urged to contact Bray Garda Station on 01 6665300.