He can't.
If I extrapolate data from animal studies, a toxic dose (toxic does not mean a person will die) would require 18,200 91,000 mg of Xanax for toxicity to arise.
Xanax is one of the safest substances and 0.25 mg tablets are not going to kill him. Notwithstanding always call for medical assistance after a suicide attempt or an overdose of Xanax that causes unconsciousness.
And you're going to help him overdose? Some friend you are..
Bad selection of a drug to committ suicide with They usually just sleep for three days wake up wet and dirty.
Immediate Medical Attention Is The Best Course Of Action. Whether Possible, Determine What Other Drugs Have Been Taken And Notify Medical Personnel.