Are they just allowed to break into someone's home like that?
Old man was probably scared for his life, maybe even disoriented from pain medication.
Yeah, this is one that falls both on the cops and the relatives. The relatives should've went over on their own or called one of the neighbours to look in on him.
Those "welfare check" things are basically just a step down from a search warrant. I'm sure the family whined on the phone that the guy was sick and just out of the hospital, and they finally went over thinking they'd find a dead body. Next thing you know, an old man that probably just wanted to be left alone is dead.