Under no circumstances can or should a post here be a substitute for qualified on-site medical advice. If any symptoms of poisoning are observed, contact your local healthcare provider.
After the update:
This is elderberry (Sambucus nigra). The berries contain low doses of cyanogenic glycosides (which produce prussic acid) and lectins.
Typical symptoms of raw elderberry consumption are queasiness and vomiting, GI issues, stomach cramps and diarrhea, mostly caused by the lectins. The larger the dose and the more sensitive the consumer, the worse the symptoms. If the symptoms are treated, no permanent damage is to be expected. The amount of prussic acid in the berries is comparatively low, some sources give 200 berries per kg of body weight as uncritical. These numbers should be treated as reference only, as with all plants, contents can vary both during the season and between individual plants. Likewise, children and adults with weaker constitution will tolerate less.
Note that cooking destroys the critical compounds, making the berries safe for human consumption (not to mention delicious).