How do I get all the tweets with a keyword from a specific date range?

I am a HCI graduate student doing research in Information Visualization. I am trying to get all the messages that were tweeted since October 14 until today (October 16) with the tag #ParoPR (an islandwide protest from Puerto Rico against the government). I am receiving only 1,500 tweets, the limit. Is there any possibility of getting all these results so I can analyze them?

Thanks