Wow, that's quite some nerve to steal voting papers and vote on behalf of people! Hopefully this is publicised enough that no one votes for those candidates, I'm not sure you could meet the burden of proof required to actually prosecute them.
Interesting that this was picked up by a petition and not from people double-voting. Surely some of these people would want to vote but didn't get voting papers, and so would ask for new ones, then be identified as having voted twice?