How to deal with grief and guilt after losing my grandfather in our home?

I’m 27, and for the past few years I’ve been living part-time with my grandpa— always staying at his house from Sunday to Monday for work. He passed away two days ago at 85. 9 days ago, I came back into town and was in my bedroom when I heard his friend come by with food. My grandpa refused and was frustrated that his friend was trying to be helpful. I checked on him later, he told me, “I’m going down, but I don’t want to talk about it. How are you? How’s your boyfriend?” I kept the conversation normal, but I knew then that I needed to prepare myself.I told my family what I noticed and said that he might be nearing the end, especially since he wasn’t eating. My mom and I went to get him some easy foods that he liked and he was grateful for that.I went back to my other home and returned on Thanksgiving night around 10 PM. I put leftovers in the fridge and noticed the food and water my mother and I brought were untouched. His light was on, and he seemed to be struggling to get in or out of bed. I asked how he was doing and let him know that I put the thanksgiving leftovers in the fridge and asked if he needed help. His answers were short, almost like he didn’t want me lingering which is unusual because even late at night, we would sometimes have a short conversation. I could tell he didn’t want me “fussing” or worrying, so I carried on like normal and went to my room crying myself to sleep.The next day my parents and I went to check on him. They asked him if he’s hungry, why he wasn’t eating, if he needed a caregiver, and told him he needed to try to something or they’d have to call a doctor. He became very frustrated with them and refused all help and told them to just leave him alone, he wasn’t being very nice. But I understood his frustration. He didn’t know I was there, I stayed away from his room (sad, avoiding, not wanting to embarrass him,etc). He had said he’d lost his will to live. I was feeling very protective over him, I just wanted his passing to be comfortable and non-invasive.It was an incredibly hard 9 days, knowing what was coming. But by Saturday, after mentally preparing myself, I finally felt some peace—still very sad, but accepting. I came home late around 10:30 or 11. The house is always pitch black at night, so I used my phone to light the way, turning it off when I passed his room so I wouldn’t wake him. After I went to bed, I heard the cat meow a couple of times and then stop—unusual but not exactly uncommon so I didn’t get up. The next morning, I woke up late, walked past my grandpa’s room to clean my bathroom for about two hours, then showered and went to my room to get ready for the day, taking my time. I think I was scared and avoiding the possibility that he might have passed. When I finally checked on him, his bed was empty, and I found him lying on the floor at the foot of his bed. My heart dropped. “Grandpa?” but there was no response—no movement, no breathing. I fell to my knees next to him, crying my eyes out. The guilt, pain, heartbreak, and grief hit all at once. I called my parents immediately, and everything was handled from there.I knew this moment was coming, but the hardest part is knowing he didn’t pass in his bed. And the guilt of not knowing when he fell or how long he was on the floor alive before he passed, my biggest fear was finding him on the floor and him dying alone and scared. I feel so irresponsible that I didn’t peek into his room when I heard the cat, not checking on him when I first woke up in the morning. What if he fell shortly before I got home and was still alive?What if he fell while I was at home?What if I could have been there with him when he passed?Even if he already passed by the time I got home, it hurts knowing that he was laying on the floor dead for so long.I regret not saying bye to him when I left that day.The guilt of carrying on and leaving him alone like he said he wanted.I feel I should've made more effort to see and talk to him in his last days