New Rebels bikie president Jamie Ginn has died suddenly at the Perth Watch House.
Gang Crime Squad detectives took the 50-year-old into custody in Gnangara around 1pm on Tuesday.
He was then taken to the Perth Watch House where he was charged with a number of drug and firearm offences.
Around 7pm, Ginn reportedly had a seizure inside his cell.
"Immediate medical assistance was provided until the arrival of St John WA, however, the man could not be revived," a WA Police spokesperson said.
"The death is not being treated as suspicious and as per standard protocol officers from the Major Crime Division will prepare a report for the Coroner."
Ginn's death comes less than a week after an alleged gangland shooting in Baldivis.
Two Rebels bikies have been charged over the alleged shooting that targeted Mongols bikie Adam Wragg.
Early voting for Secret Harbour by-election begins Monday
Welfare concerns for missing Swedish national last seen in Warnbro
Wanted man last seen in Golden Bay
Passenger critically injured in West Pinjarra crash
Unregistered painter fined for requesting hefty deposit from Singleton homeowner and not doing the job
Police hunt driver following dangerous Baldivis pursuit
Welfare concerns for boy last seen at Port Kennedy skate park
Rubbish truck catches fire in Baldivis
Driver injured in bus crash in Rockingham