Who called from 2815019618

Got a call from this number this morning. I picked up, but did not say anything. At first I heard
heavy breathing(no crime), then the male foreign said very clearly; "I'll killl you".  I hung up and 2 minutes later got a call from 281-416-5576. Again, I said nothing and just heard heavy breathing..
Houston area code, but probably coming from overseas. Why is there not some government department
that can track and close these ****heads?

Received calls from this number and have been hung up on every time I answer or call it back.