I have been accused of a very serious charge by a man whom…

If there's a warrant for your arrest for an armed robbery, do not say anything further to the police, as it's clear that they don't believe you and anything you say to them won't stop the warrant and can be used against you in court besides.

Get yourself the name and phone number of a good criminal lawyer, so that if you are arrested, you have someone you have a lawyer who can step right in and protect your rights. You're not going to have time to look for one once the police are already at your door.

Here's the definition of a robbery in the state of California with the elements that would have to be proved.

https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=PEN&sectionNum=211

The robbery statutes continue through PC 215 which would have additional elements depending on the facts and circumstances of your case. Possession of a firearm during the course of a robbery adds a ten year enhancement of your sentence upon conviction.

Though all of this sounds and is serious, you don't have to prove your innocence. You start off as innocent under US law. It is the prosecutor that must prove you guilty beyond a reasonable doubt by proving every element of the crime charged. The best thing you can do for yourself at this point is to refrain from talking about this incident and to get yourself a good lawyer, to whom you will tell of the complanant's extortion and his prior history. That information will be helpful for your defense, as is the fact that there will be no gun.

Just checking in to see if you need more help or any clarification of my answer. If so, please reply here on this question thread.