Adult2Adult Night Talk: What quick steps should a husband take if the wife suddenly tells him that she isn’t interested in their marriage anymore?

There’s no record of any previous misunderstanding. They have been doing comfortably well. The wife simply woke up and said to her husband of five years, “I am not just feeling the marriage anymore. Sincerely, the love I had for you died many months ago. I have tried my best to revive it, but it can’t work. I am so sorry, dear, I can’t continue in this marriage please.” And she walked away. She walked away from the marriage – from the husband and their two children.

What quick steps could the man take? Please only serious advice is needed. Thank you.