In The Garden: Ragged leaves, little berries, mingles with herbs

Hello all! My brother is currently cultivating a small herb garden at work. In one planter, he started two oregano plants from seeds. The first turned out fine, but the second looks nothing like oregano and is now sprouting berries.

Having used soil from his backyard garden, he suspects that a foreign seed sneaked its way into his planter and overtook his second oregano plant. Before he excises the intruder, he'd like to know what kind of plant it is.

I've attached pictures of the plant to this post. Any ideas? Thanks in advance!

 

Solanum nigrum or close relative.

 

Thanks!