He kills women.
4 seconds sound clip from the The Silence of the Lambs movie soundboard.
You can hear this line at 01:08:50 in the Blu-ray version of the movie.
Quote context
[...]
- Everything you need to find him is right there in those pages.
- First principles, Clarice. Simplicity. Read Marcus Aurelius.
- Of each particular thing, ask, what is it in itself? What is its nature?
- What does he do, this man you seek?
- What is the first and principal thing he does?
- What needs does he serve by killing?
- Anger.
- Um... social acceptance and, um, sexual frustration, sir.
[...]