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arrest warrant – Please Help?

My brother was involved in a rear-ended accident. He was carrying a high-end mountain bike in the back of his truck (via a bike rack), and the collision caused the carbon fiber frame to cracked. Here's the problem:
He bought the bike at a local bike shop a few years back. The owner of this bike shop has two different businesses: sport shop and gun shop (at two different locations). Recently they chose to close the sport shop, which was selling bikes (my brother's included), and only have the gun shop opened.
When dealing with insurance company, my brother submitted the receipt from the sport shop when he bought the bike, as proof of ownership. After getting this copy, the insurance company went to the gun shop and talked to the owner, verifying the receipt and the amount are both correct. Unfortunately for my brother, the shop owner does not recall the transaction. And when asked to look into the system, he could not find my brother's transaction either. BUT he also indicated that during the sport shop closing down, the database from that shop was not completely transferred, and my brother's transaction might be lost during the merging.

The insurance company denied to claim, and then went to District Attorney to file a Fraudulent case against him. Just few days ago, my brother received a letter from the District Attorney office, notifying him that an arrest warrant has been filed against him, and asked him to call the Sheriff office to schedule a self-surrender!!!

Any information or input to help my brother will be GREATLY appreciated! He's innocent, and is completely freaking out right now! Thank you!

Does this arrest warrant means he will be detained in jail until proven NOT guilty, or he just needs to come in for questioning, then will be release after 24 or 48 hours? Because he's never done anything illegal, and jail time would freak him out.

Another thing: few years back when he bought the bike, he paid everything in CASH (part of the deal from the bike shop, gave him free components because they can avoid the Credit card's commission charge). That's the problem.

Also, he just lost the job 8 months ago, and does not have enough money for a private attorney. Should it safe to turn himself in alone? Any assistant, like public defender maybe?

Questioning, then he will be released, or they will keep him there?

Since the insurance company could not locate my brother's transaction from the bike shop, they automatically declared that the receipt he submitted was altered and fake!! That's the bottom line of his problem: Insurance company filed a Fraudulent claim with the DA because they believe he submitted a phony receipt. And the DA believes them!! He went to asked the shop owner to write a statement for him, regarding the missing information during the merge, he said he does not want to be involved.
HE JUST CALLED THE SHOP OWNER, AND NOW THEY TOLD HIM THAT THEY COULD NOT FIND HIS TRANSACTION, AND NEVER CARRY SUCH BIKE BRAND. NOW ALL THE EVIDENCES ARE AGAINST HIM. IS THIS WHY THE POLICE BELIEVE THEY HAVE A CASE AGAINST HIM?

If he turns himself in, which he will definitely, how long will they hold him in custody? weeks, months??? Please help!!