He had been keeping an eye on her for some time now so he would be able to predict her movements. Naturally, he was also aware that she was armed, so he kept himself hidden and waited, intending to strike quickly, before she has time to react, although he could try to disarm her if necessary.

He hid himself around a corner, leaning casually against the wall as he waited for her to walk by.

Why should she expect anyone else? They were the only ones around, for the time being, and he was not so foolish as to blow his cover by stepping out.

As soon as she was within sight, he reached out to grab her around the shoulders and drag her in front of him, so she won't glimpse his face, pulling her in and using his other hand to try to bring a wet, pungent cloth up to her face.