It's understood the prop gun that was fired was a double-barrelled shotgun but Detective Inspector Tom Armitt said several firearms were inside the bar when they arrived.
Workplace Health and Safety is also investigating whether proper protocol was followed in the wake of the tragedy.
Bliss N Eso, a well-known hip-hop group, have since confirmed the filming was for one of their tracks.
"We are able to confirm the death of a person occurred today at the filming of a Bliss n Eso music clip," the statement read.
"The band were not on site at the time. The video production crew and our team are currently working with the police in their investigation and we are unable to provide further comment at this time."
Police confirmed the man killed was an actor and not a member of the band. No one else was injured, while another young man was led away from the scene by police.
"A scene was being conducted during which the actors were using firearms," Det. Insp. Armitt said.
"As a result of the use of those firearms one of the actors received wounds to the chest and subsequently died from the injuries."
He would not confirm if live ammunition was being used during the filming.
"A number of firearms were being used during the scene, I can't (say) whether they were live or real firearms or the type of ammunition being used.
"The man has suffered injuries to the chest ... how that occurred is part of the investigation."
Construction worker Blake Shaw, who was on the floor above, said he heard loud bangs, one after the other, at about 2pm.
"There was like three gunshots and then about five minutes all the cops came," he said.
Mr Shaw said from a hole in the floor he could see money strewn around the bar and the man's torso covered in blood.
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"We could see them (paramedics) working on the guy."
Bliss N Eso had been advertising for a range of people to help feature in the film clip for their track Friend Like You, which was being filmed in Brisbane and the Gold Coast.
Among the acting roles advertised were for an Asian male aged 11-16, a white male drug dealer aged in his 30s, a homeless man and a white male businessman aged late 30s.
The Brooklyn Standard was closed to the public for today's filming.
A report will be prepared for the coroner.
Police had earlier a man died "following a workplace incident", saying the shooting appeared to be accidental.
The Brooklyn Standard this afternoon released a statement.
"After an incident at Brooklyn Standard today, our doors will remain closed tonight as a police investigation is undertaken to identify what happened within the bar," the statement read.
"The incident occurred during a film shoot at the venue, for which Brooklyn Standard had been wholly rented out, outside of opening hours."
Filming for the sequel to Pacific Rim took place nearby yesterday but the movie's producers have said they were not filming in the area today.
Careers & Course Advisor Annalise Helibronn said she and her students were left traumatised by the shooting and feared a classmate had been killed.
It's very upsetting," she said. "Everybody was a bit freaked out."
"I came out on my 10-minute break and saw it all this happening. I work at a college, and we were scared that it was one of the chefs we work with but later found it was someone in the (music) film.
Ms Helibronn said they initially dismissed the sirens as it was pretty usual to have a police presence in the CBD.
"I heard the sirens going off and I first thought it was normal thing being in the city," she said.
"Then I saw four ambulances and a lot of police cars and people sitting in the alleyway who looked distraught as well."
"It was heartbreaking and shocking .... There is so much going through your head, like what is this world coming to?"
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James Rouse, who works across the road at Hymans Valuers and Auctioneers, said they were aware of filming going on in the area but only realised someone was shot when police turned up.
"I didn't hear anything," he said.
"I walked up the street after seeing an ambulance and police and then heard about the shooting.
"I've worked in the city for 20 years and never heard of a shooting or anything remotely like this happening in the CBD."
