Is it normal to think about being murdered every day?

It's a long story. One member of my own family was caught cheating through text message by his own wife. That night, the wife confronted her husband about it in the kitchen and totally roasted him to total humiliation.

Her husband was critically mad about the confrontation and started throwing stuff out of fury and picked up a meat cleaver at the kitchen and threatened to hacked his own wife with it. We knew he would actually do it if the wife didn't stay silent. He sort of lost control over himself. Then, my big sis came to stop him and he choked my sis with his hands.

Then, he realized the horrible thing he's doing after my sis was screaming as he strangled her so he stopped that crazy shit he's commiting. I was still a wimpy teenager back then and saw the incident. I feel guilty because I was too afraid to stop him unlike my heroic sis and is still very traumatized by the incident.