Exemption from Election Duty

my brother is an asst. primary teacher. he is contesting from gram panchayat seat as an INDEPENDENT candidate. but he is appointed as a 2nd polling officer. he produced all the supportive documents to support his candidature to the DPEO. therefore he did not attain the training. but unfortunately show-cause letter is given to him. is a candidate bound to perform election duty? what is the rule regarding a candidate? what should he do now? please reply quickly.