The Salvatore Culosi accidental shooting case has been settled with Fairfax County for $2 Million.

The real story there goes like this:

They went out to serve a warrant on a nonviolent gambling suspect.

More than a suspect, since the cops had been placing bets and dealing with him for a while. 

So, to serve the warrant, they take out the whole swat team and swarm his front yard.  While they are taking him out with no resistance whatsoever, one of the guns accidentally goes off. 

Why did they take a heavily armed SWAT team out for such a simple warrant service?

Because the HAVE a heavily armed SWAT team.    And they have nothing better to do.