I agree that it does look a lot like elder, but as you've figured out by now, the arrangement of the berries is completely wrong - elderberries grow in big sprays. Also, the berries look a little bigger than elderberries.
I know this doesn't contribute to identifying your plant - I just thought I'd say you weren't far off with elder, at least as far as that sprig goes. I'm now going to go an look up pokeweed
- I love learning about new plants!