Sometimes you can't figure out why a panic is happening, but what you can see is how the people react to it by looking at the volume. Usually when you see something drop in price, a lot of volume come with it but sometimes you will see a drop that had little volume involved. This is not really a panic yet because it was most like 1 person that just sold their position. So if you see a price drop below the base, just look at the volume. If the volume is low, keep watching it as it might continue to keep dropping until it panics the holders. You will literally see people selling tons of bitcoin on the order history and this should tell you that this is indeed the panic.
Now how to know where to buy in a drop/panic. The price should keep dropping until it hits a lower support line and bounce back up. Best thing I like to do is put a buy order.
https://www.coinigy.com/s/i/599b17b66ac02/
for example if you see this chart, the yellow line represents your base, the violet line represents the last base and is the area you want to buy . Anything below that is just a gift . You really want to buy some there if you can. You can see in the light blue I circled the volume that shows a lot was sold. Without that volume I wouldn't participate because that is telling me there are no buyers at all since it was able to drop so low in price without much volume. Always pay attention to the volume because low volume usually leads to the price dropping even further until the the real panic happens.