Hey there!
I believe he should "Ask someone to sit in for him while he took his phone in response to the message".
If it is supposedly an urgent message, something bad could have happened, so he should probably check it just in case. That rules out option one. I think he should ask someone to sit in for him, so that way the interview still stays going. If he excuses himself to check the message, then the interview has to stop. If he cuts the interview short, that is not polite or the best choice. Therefore, the second option is correct.
Have a terrificly amazing day! :D