My Only Brother Passed Away Very Suddenly And Tragically One

My only brother passed away very suddenly and tragically one month ago. He was only 47 yrs young. We found him on the kitchen floor, unresponsive. We administered CPR immediately and when EMT arrived they attempted and in the ER at the hospital too. We don't know for sure did he fall backwards pass out, an instant heart attack? Did he slump to the floor and lie down and die? When I started CPR on him his eyes were half open and he looked calm. He was complaining of severe heartburn for a couple weeks off and on prior. He did struggle with alcohol abuse but had been sober for over a year. He had two hip replacements and osteoarthritis in the knee. If you had to give your opinion on what happened, what would it be? I am so devastated that I couldn't save him.