Police officers were watching CCTV camera footage of the fight between two groups near the food court of the Valley Centre above Fortitude Valley Station about 4am on Monday.
"On closer examination they saw a male person lying on the ground and persons nearby had blood on them," Inspector Sean Cryer told reporters.
"We immediately dispatched the Queensland ambulance and uniformed crews to the railway station."Â
A 24-year-old man was found with injuries and people who had been part of his group by his side.
Despite the efforts of paramedics to resuscitate him, the man died at the scene.
"Unfortunately the male could not be saved, and he was declared life extinct at the scene, and we'd like to extend our condolences to his family," Insp Cryer said.
Onlookers told the officers that three people had run away and down into the train station, so they chased after them.
Insp Cryer said they found the trio on a platform along with a weapon and they were arrested.
The three were being questioned by detectives, but he said the initial fight was not gang-related.
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