What is this tree and what are these berries?

[Undertoad]

This tree grew spontaneously in my back yard, around the tree that was actually planned for that area but died. For years it shared space with a pine tree but this year the pine finally died for certain. Now this tree is doing great.



But Jacquelita ate some of these berries just now (the ripe dark ones not the red ones) and I need to know if she is going to die.

Thanks in advance