The incident took place at the booth at Project Girls School and Kumar had cast his vote before it, Station House Officer of Bhakhtiyarpur police station Vinay Krishna said.
An elderly who was among those injured by the primate, however, returned to the booth to cast her vote.
A team of forest department rushed in from Patna and attempted to nab the monkey but fauiled. The menace did not recur later in the day thanks to vigilant forest officials, the SHO said.