This happens all the time but you often hear of patients who hang onto life until after their family leave because they can’t stand seeing their sorrow. 
Don’t beat yourself up about it.

Davek is correct in what he says. I know someone who died half an hour after here daughter left the care home where she lived. 

Sorry to hear about your dad.

My dad was actively dying due to cancer for 5 full days. This started only 5 days after being diagnosed with terminal cancer which was very shocking and I was emotionally drained before he began to die.

I spent everyday at the hospital with him but I needed rest as it was so exhausting. I therefore went home every night to sleep.

I had to tell myself that I couldn’t be there all the time and that he would know that I was there everyday with him anyway.

if he was like my dad, the end would have been peaceful and sedated and seemingly ‘unaware’ of his surroundings. 

and like others have said, it is a very real thing that death happens when loved ones go