Flash player uses large amount of memory after leaving website

I'm using a laptop that runs Windows 7. I visited a website (2016 North Carolina Elections, Primary, Candidates, Races and Voting) using Firefox version 44.0.2 and noticed that my computer started heating up. I box popped up that said a script on the page stopped working. I left the page and checked my running processes on the task manager. It said that FlashPlayerPlugin_20_0_0_306 was using 1.4 GB of RAM. I closed out Firefox (and had no other browser windows open) and it continued to use up a ton of RAM. I eventually had to end the process. Any idea what happened and how to avoid this happening again?