Man, I gotta start getting on here earlier. OK,
Step 1 - Get home. Oh, wait, I work from home most of the time, including now.
Step 2 - Grab the gear:

Not quite everything, I'd grab:
both SKSs
Mini-14
both Mosin-Nagants (M91-30 M44)
K31
10/22 (Scoped, accurized, and can take any game in North America out to 50 yards, technically. Plus, I've got like 2500 rounds for it, which weigh next to nothing.)
30.30
Glock 21C (.45 ACP, full size, factory compensated)
Rossi .357 Magnum (not pictured)
H&K USP Compact .40 (not pictured)

Both shotguns, of course.

That's about half the ammo - I've got:
2500 rds .22 (cheap, light, deadly, accurate)
990 rds 7.62 X 54R (for the M-Ns)
1000 rds 5.56 NATO (as you can see, 120 rounds are in speed-loaders, ready to fill the 40rd mags in the pic)
1000 rds 7.62 X 39 (for the SKSs)
500 rds each, .45, .357 magnum, .40 ACP, 12ga (various 12 ga, mostly birdshot, but a fair amount of 4 buck, 00 buck, slug, and Rhodesian Jungle, 00 mixed with 4 buck)
300 rounds 7.5mm Swiss (1000m rifle)

I pulled out the big stuff so you could see. This pack is always ready to go:
'Rambo' knife (compass, survival kit, threads onto pole to become spearhead)
cooking gear
stove
food - 3 people, 3 days
AR-7 (it's in pieces in the buttstock you see, which is watertight and floats, .22lr)
PUR water purification pump
cold weather kit
tent
sleeping bag
Leatherman
Then, I'd make for this building:

Which is less than two miles from my house. 18 Floors, only two staircases to cut out at the 2nd floor, lots of room to set up shop.
Now, if I only had the resources to stash a helicopter on the roof...