Music by Kevin MacLeod. Available under the Creative Commons Attribution 3.0 Unported license. Download link:  https://incompetech.com/music/royalty-free/index.html?isrc=USUAN1200056

MacLeod's description:

Genre: Soundtrack
Length: 3:12
Instruments: Strings
Tempo: 90

I piece unlike anything I've done, this is a very difficult piece to process emotionally. It just never lets the audience rest. There are a lot of uses for this sort of piece. It is also available with percussion, which gives it a more immediacy. ISRC: US-UAN-12-00056 Dark, Intense, Suspenseful, Unnerving 2012