Is it normal for my parents to argue for awhile now?

So my parents and I went on vacation together on Friday while my older brother stayed home alone for the weekend, Monday and Tuesday. When we got back, we noticed little things that were different. The glass table next to the hot tub was gone, with a chipped outlet on the wall. He had slipped coming out of the hot tub apparently and broke the glass table(He texted my dad about it, but he didn't say what day it had happened). Earlier on the trip, my mother had asked him to turn off her laptop, but we saw that the laptop was left to die. Her business card for her laptop was jammed into her laptop so bad that we had to use pliers to get it out. There was 8 cups of coffee made in the coffee maker, left there cold. The kitchen was a mess from looking like someone had cooked something without cleaning up. I had stepped on a thumbtack in the living room, thinking we never use thumbtacks. Some photos on the walls were rearranged and moved. There was a crack in the downstairs door. Our couches and blankets smelled different than before. He had also lied about there being a two hour delay on Monday, because there was none. The TV doesn't work anymore, and I saw the volume was put all the way up.

We noticed all of these things in the one night were back from vacation, while my brother was not at home. He's been coming home at 11:00pm ever since we came back. I know all of these things are assumptions, but that's all we can do. My mother has a hard time asking him things because with him, he denies everything. She asked him if he had friends over, "no." Which was obviously a lie, because my friend who lives two houses away said she had seen him with a guy and a girl. I know you might think that were assuming all of these things, but trust me, it all adds up.

My brother has been bringing friends over after school sometimes when he isn't suppose to. I don't tell my parents, because I know he doesn't want me to. Now, it's just too much. My parents have been arguing every since, which has been about 4 days. My dad is on my brothers side, denying everything, covering up for my brother. My mom has a hard time believing all these excuses from both of them. Every argument is getting more and more intense, and it's really getting me worried. Is this normal? Please, please please help me. I don't know what to do anymore.