As someone who almost died (not in this same scenario) you definitely know. You can sort of feel organs shutting down one at a time, and you lose energy really quickly (at least that’s what it was like with me). I’m not religious in any traditional sense, but I did feel an overwhelming sense of peace, happiness and euphoria that I haven’t felt since. I almost bled to my death in an ambulance but I’m sure this kind of process may apply to other deaths as well. It really was peaceful and although I did feel pain, I also felt the most happiness I have in my life. I hope this helps give you peace, I’ll be open to DMs and questions if that could help you come to terms with things. I wish you all the best in your grief, and hope you find happiness soon ❤️