Song by American band Imagine Dragons.
Apparently, "The song was inspired by lead singer Dan Reynolds’ sister-in-law (his brother's wife), Alisha Durtschi Reynolds, who died from cancer, Reynolds said in a press: "She was the brightest light. A beacon of joy and strength for everyone she met. Her sudden passing has shaken me in ways that I still am unable to express. I was with her and my brother when she passed, and it was the first time in my life that I had witnessed death in this way. It sealed into my mind the fragility of life and finality of this all.{....}"
(https://www.nme.com/news/music/imagine-dragons-announce-new-album-mercury-act-1-share-single-wrecked-2983702)
Exactly that. Being there, holding a love one's hand during their last moments. And see life just cease. Witness it. One moment he is there alive, the next .. he is gone..
"First time I had witness death in this way".. My thoughts exactly now that I think of it. And all the more shocking, devastating. Unbelievable at first. Surely he will wake up?
But then, he doesn't. It's finished. Just like that.