I helped a friend dismantle a shed in a pasture with three alpacas on his hobby farm. When we looked in their direction, they froze like statues. When we focused on the boards, they would inch just a liiiiittle bit closer, and freeze when we looked again. There was an ungulate serial killer vibe happening.
Apparently they get quite irritable close to shearing time, because the wool droops down in front of their eyes and the stumble into each other.