Was my best friend fucking my mom?

Me 13 my best friend 14. He was sleeping over my house one night while my dad was away on a fishing trip with his college buddies. My mom went to bed before my friend and I did but it was weird because she never sleeps without my dad. My friend was sleeping on the couch in the living room and I could hear him moving around. I was in my bedroom sleeping when I heard him get up and walk around. It was 3am and he was in a robe my mom left which was completely weird because we both had robes to use. He walked in through my door and then left immediately and walked down the hallway towards my mom’s room. I was wondering why he was doing this and I peeked through the door and saw him get into bed with my mom. I ran away before I saw anything else. We’re still friends and I haven’t brought it up to him but I could never look at him or my mom the same ever again. I love my mom but she’s been in the comments of every hot guy on tiktok. I have a feeling they’ve slept together. I’ve lost my best friend who was once a good guy. How do we get through this??