Product: Checking or savings account

XX/XX/year> This case is in regards to my small business account with Citibank. Ive had a small business bank account with Citi for 12 years. On XX/XX/XXXX, I noticed a transaction seemingly going to the IRS for {$37000.00} that I did not make. I called Citi right away and filed a claim. 
I dont know how somebody got into my bank account and was able to make this ACH transaction. I never gave my info to anybody. Further, to Citis lack of security systems, I never received a confirmation or request for approval from Citi the day the $ XXXX transaction was made. And this was a very large transaction that should have been unusual in my account. The only way I realized was when I logged into my account a week later and saw the missing funds. 
Since XXXX, I have been fighting with Citi for them to give me my money back. I filed a police report as well. Citi has not collaborated with the XXXXXXXX XXXX police department. Yesterday the police served them with a search warrant. 
In the last 2 months, Ive had a terrible experience with Citi. I spoke with multiple people all to no help. Thanks to my accountant, I was able to get a transcript from the IRS showing the payments Ive done to the IRS ( associated with my SSN ) and there was no payment for {$37000.00}. I provided this info to Citi hoping it would solve the case. It didnt. On XX/XX/XXXX they mailed me a letter denying my claim, saying time had run out and they had not been able to get a hold of the IRS ( as they believe thats where the money went nor the police or I think the money went to the IRS ). 
I got my case re-opened within Citi, but its with the same fraud department that denied the claim a few weeks ago and they dont seem to be doing much to solve the case. They mentioned that they were not able to get a hold of the IRS. I called the IRS last week and was able to get some info on the phone, all confirming that the transaction is not legit/they never got that payment from my account or SSN, nor even that payment matching the confirmation number that shows up on my statement. Unfortunately, I dont have this info in writing, Im trying to get a hold of the IRS again to start a hard trace investigation but getting to talk to a human has not been easy. 
Citi claims that until they are refunded the money by the other bank they wont give me the money. Whoever stole my money will clearly not give Citi the money back. On my last conversation with Citi last week, I was told to solve the case myself because for them getting a hold of the IRS had been hard. This is ridiculous as its clearly a scam/fraud due to their bad IT security that enabled somebody to get into my account and steal a large amount of money. I dont understand how can somebody have money safely in a bank, that money can disappear due to the Banks lack of security, and the bank wont protect the customer and refund the money. 
Please help investigate this case so that I can be refunded. The loss of $ XXXX has put a significant strain on my small business and I spend multiple hours a day trying to solve this case, which also hurts my business. 
Thank you very much for your help. Please contact me for any info you need. 
Best, XXXX XXXX