Skeleton started shooting me through an oak door

I was playing on my realm, and I live in the small village library. It turned nighttime, and I went back to the library, and blocked the doors with my recently obtained moss blocks. Then I tried to go to bed, but there were monsters nearby. So I opened the door to see where they were, and saw a skeleton. I then shut the door because I really despise them. After that, he started shooting me through the door!