getting a call from their son calling to say that he is ok and not to worry with zero context
So, funny/sad story, I did the exact same thing during the shooting at the college I was attending. (We don't live in the States, so this is definitely not a common occurrence here!) My family only had one cell phone, and as luck would have it, I had it that day. I called my mom at work to tell her I was ok and in a safe place. My mom was very confused during the call. She later told me that after we hung up and she processed what I had just told her (and heard the news on the radio) she almost went hysterical.