Embezzling Problem

What should I do? For background, my husband has a restaurant with 2 more business partners (a cousin and aunt). They all have equal parts of the business… or so we thought. A couple of years ago, we noticed my husbands checks getting smaller, 50% smaller, while they seemed to get more luxurious items, which would’ve been impossible with the checks each were getting. We didn’t think too much since the cousins husband was also working for the restaurant as an employee. Note: the aunt, which is the cousins mom doesn’t work and lets the daughter manage her share. One day my husband stumbled upon the checkbook and noticed several checks made to the cousin and the husband separately. He was also withdrawing money from it. We asked and they said it was to pay staff. To clarify, my husband has been working the kitchen and they do front of the house and financials. They had never showed my husband any financial records other than the business account. Fast forward Covid hit and we were able to stay afloat pretty good. Being a popular restaurant in town, we were still busy on takeout and curbside. Checks were coming in as if Covid hadn’t hit just enough to cover bills. In 2021, the husband came in and told my husband that they were buying a new home, Not just any home but a 900k home. There is no possible way they can afford it. They claimed his parents had given them that money. We come to find out their first house, which was 200k in debt back in 2018 was fully paid for. And they had 280k in down payment for the new house. We know for a fact the parents could not give them that much since their story changed so many times. My husband got suspicious and demanded the credit card login. We found out they were paying their own bills, car repairs, new house repairs and so much more with the company credit card. Not to mention they also took trips using this credit card. Without telling my husband I looked into more stuff and found out so much more. The parents had not paid for the house, they have been stealing over 40k cash a month and delete the transactions from the register. They still don’t want to give my husband the log ins and have not had luck. They also set up cameras in the restaurant and I have caught the husband putting cash in his wallet daily. I think they caught on and decided to eliminate the playback option. Right now my husband is struggling hard and they are living the life with brand new 80k cars and so many activities. I want to contact the IRS to kinda let them know but I want to make sure it’s the right move. My husband doesn’t know how much I know. I found out discretely because it’s sensitive info. Reddit, what should I do?