Especially since she works for the firm that was representing his Dear Leader (although he probably had no way of knowing that!) Did she do something to mess with the elevator, make it stop on every floor? I know you can do that with buttons inside the elevator but I don't think I've ever seen anything like that on the outside, in the hallway.
I mean, he attacked Ness, Luke, and Teddy when he didn't need to and ignored Amy. Everyone he attacked (including the witness, who was presumably the target, and Emily who was protecting her) was a person of color. I think we can assume that he attacked Ness just because she was a Black woman and there was no one else in the stairway to stop him.