Please help

I think my dad has been secretly drinking. His side of the family is full of alcoholics and my grandma (his mother) is hardly involved in our lives because of this. He has seen what addiction does to people and yet he is doing this. My suspicions started a couple months ago when I smelt alcohol on his breath in the middle of the day. Something about this specific moment made me start thinking about all the other times I smelt alcohol on him or his odd behaviors that someone who is slightly intoxicated would do. Then a couple months ago my mother found an empty beer can under their bed. It was kind of made as a joke and he was kind of awkward and standoffish to it. Then I started digging and would find empty cans in the trash can as if they were hidden in there. One day I smelt the alcohol and got the courage to say something to my mom. She didn’t say anything other than she would check and we didn’t speak of it again. Then tonight about an hour ago I was in my room when I heard two loud bangs like someone slamming doors closed. I came out of my room to find my mom crying in her study in the dark. I tried to ask what was wrong and she got mad and told me to leave her alone. I walked out to the kitchen and saw some lemonade in a jar and a bottle of vodka on the counter. I immediately knew the fight was over alcohol. I went back to my mom and said was it because of alcohol and she said yes. This started a conversation between us about my dad and him potentially secretly drinking. She then tells me not only have I told her about it but my little sister has also come to her about smelling alcohol on my dad. That she herself has also smelt it too and she has been slightly suspicious. She tells me that before she found out my dad was using dip he hid it from her for 1.5 years and the only reason she found out was because she saw it in his work bag. I asked her if she checked his bag yet and she said no. I did and I found an empty can of alcohol in his bag. Immediately we start looking around the house trying to find more and luckily we didn’t find anything but she texted my dad and said you need to come home. He called her and said he was not coming home and they talked on the phone. I couldnt hear it all but I heard her say he needs to be honest and that we know. When they got off the phone I asked her what he said and he basically attacked her by saying all these horrible mean things that I know he doesn’t mean. She said hes been drinking because he is slurring his words and I told her this is what alcoholics do. They say the nastiest rudest most meanest things because they feel like they are being attacked and it’s their only line of defense. He got home and came in and I stood in the hall and he sat down on the couch. I sat down on the couch as well and we sat in silence for a bit and then my mom said well? He asked for them to talk in the other room and I said no I want to be present and he said no. They have been in the other room for an hour or so now and I am just on edge. He is saying the meanest things to my mom and literally idek what to do anymore.