He or she won't stop texting me saying things that's harassing and scary me. He or she is saying their a cop to get to me.. HELP

Call your local LE and also your phone service provider and file complaints. The phone service provider should be able to block the call.  Consider getting a call blocking device or phone.. You can google them and many are around $50.00 or so. If its a cell phone, some already have call blocking, if not, there are free apps on the web that will work for some. You can google this. If you have a smart phone, there is a free app called call control. Iphones appear to have apps also. Another one is called Mr. Number.

http://800notes.com/arts/I2neMkbUAAo/where-to-report-phone-crime