Question for pilots

[Oeditpus Rex]

or just people who know about air traffic and stuff:

I live a couple miles from a CalFire air base, and a few minutes ago I saw what appeared to be a water/chemical tanker and another aircraft in tandem on a departure circle (no doubt en route to the fire in the Santa Cruz Mountains) and two other aircraft in tandem on approach. The two departing were in what looked like a refueling formation while the two on approach were in a leader-wingman element.

Can't figure why (a.) they'd be approaching or departing in tandem, and (2.) why the departing craft would be in that formation. Any ideas?