Mentally ill and drug addicted

Hello: I'm wondering if anyone can give me some information please and/or advice. I need to know what crisis response might be available for someone with a severe mental illness who is also under the influence of drugs? Will a call to 000 take a person like that to a hospital psych ward where, ultimately, they would undergo withdrawals? I have a terrible situation with my son; he owes money to a drug dealer who lives in his complex...a housing department property...and he has been threatened by an accomplice of this dealer, another dealer, to pay up money my son owes them...they have threatened physical violence and to break into his apartment and harm his cat...the thing he loves most. My son wants to continue on, however...he wants to remain on the drug...meth. And he will not testify against the drug dealer. And of course, it's a weekend. My son is in Brisbane. I feel I can't go to the police in the first instance, as it's likely nothing would happen to the dealer; and certainly not to his accomplice who doesn't live there....thus leaving my son there in harm's way. My son's pension was all used up in less than 24 hours...more than half of it went to pay off his dealer bill...but he still owes money. I just don't know where to go for help. Any thoughts, input, would be greatly appreciated.