Answer
(Fatwa: 1889/1486/D=1430)
Why the imam started weeping? If he wept because of physical pain, it will nullify the salah, the imam and the muqtadis should perform the salah again. But if he wept remembering the aakhirah or due to the fear of Jannah or Jahannam, the salah will not be nullified.
This ruling is according to the Hanafi
Allah (Subhana Wa Ta’ala) knows Best
Darul Ifta,
Darul Uloom Deoband