Am I the only one who was expecting to see..[Spoilers inside]

So around half way through the movie, it seemed like the great reveal or twist at the end would be that Dennis Quaid would be the actual killer and that he didn't know it himself out of some mental disorder or something. Hollywood has trained me to think that way. So I am glad they didn't go for the cheap twist. It was the easy way out. That the nightingale murders didn't stop at three, because Dennis Quaid's character lived on. His wife was a nurse too, just like the real killer's mother was and could've been a factor. They gave all the fake clues that pointed to this. I was surprised his son didn't even suspect this as a possibility. It was the simplest explanation.