prowler

noun2

1. •
   One who roves about for prey; one who prowls.

   • House Prees and Bloods […] were everywhere to be seen in earnest colloquy. For the matter was, that there was some sort of night-prowler about the school grounds. — 1922
2. •
   A person who moves stealthily around a place with intention to commit a crime, especially burglary or theft.

   • Discourage nighttime prowlers by installing motion-sensitive lights. — 2008