Attacking with two weapons and "Fists Full of Lead" talent from Shadows of Atlantis

How is attacking with two melee weapons or firing two hadnguns resolved?
Figures in books seem to display various examples of dual-weapon wielding characters, but I was not able to find any mechanic replicating dual-wielding fighting (Penalties?).

In Shadows of Atlantis p.223, a pre-generanted character has the “Fists full of Lead” talent (vey powerful indeed), but I have no idea where this comes from.
Maybe a Fighting Talent?

Any suggestion?