Number of bonds in a Lewis Structure [duplicate]

I'm asked to find the Lewis Structure of sulfuric acid, $SO_4H^-$. After struggling for a while, I sumply looked it up.

How can this be? Sulfur has 6 electrons in its valence shell, so it should form bonds so as to collect 2 more electrons and satisfy the octet rule. So, surely it should form 2 bonds?

But it's involved in no less than six bonds here. Huh?