Check out the strategy thread pinned at the top of the forum for details. Here's a quick summary of what you should do in your town though:
1. Send all characters possible to Burn's Summer Mansion, keep upgrading it to level 15
2. Complete the main questline for the event - check the pinned walkthrough to make sure you unlocked everything
3. Tap all criminals in your town
4. Complete the daily challenges for the event
5. Release and fight felons in your town every 4 hrs. The lose, lose, win strategy pays the most (try to kill off as many of your fighters as you can, you get a lose payout each time, then win the battle with each for the last round)
6. Visit friends to get the daily payout (30 or so) and fight three battles in a friend's town each day