Screaming neighbors with baby

My husband and I live in a apartment with eight units. The walls are paper-thin so we can hear everything that is going on around us, good or bad. Our next door neighbors are a couple probably about 19 or 20 years old, and they have a baby that has to be a year or less. Here’s what gets me. We can constantly hear the male yelling at the baby just shut up for crying. Not just telling him or her to be quiet, but going on and on for 15 or 20 minutes and slamming things around, saying that he is going to kick his or her “butt” for better a term. I’m at a standstill with this. It’s not like I have ever heard either of them lay their hands on the baby, but what is going on is definitely not okay. Babies cry, and I get that they are young parents and probably frustrated, I just don’t understand what I can do or what I should do. I know it’s not my place and I shouldn’t be listening in, but that’s not the case, it’s just that we can’t help but overhearing this on a daily basis. What should I do?