Chazzan Who Leaves During Amidah

Our congregation is without a rabbi now, and we are looking for someone to answer our question what to do when the following happens:
This past Shabbat, the chazzan during his repetition of the amidah, in the middle of a blessing, in the middle of a sentenced, seemed to get tired and stressed. Midway through a verse in the blessing for the day, he said in English “I can’t do this anymore,” and then he walked out. All of us were concerned for his health, but he returned for Mincha that day as if nothing were unusual. When we asked him if he was okay, he said everything was fine and dodged our questions on the subject. A congregant talked to his wife, who said nothing seemed out of the ordinary with him and he went to work today like normal. He is in his 50s and has grown children and no major health issues we know of.
What we would like to know is, what should a congregation do if their chazzan quits and walks out in the middle of the amidah like this? Where should they resume with a new chazzan? We had no idea what to do.