Actually, you can sprint up the stairs, get in your helicopter, and fly away. And then when you're ready you can come back and continue the mission... just never go to Downtown, they'll shoot at you there.
South Park, Charmed, Buffy The Vampire Slayer / Angel, Tru Calling, Family Guy, TrippingTheRift, FreeForAll, Futurama, Jackass, Lost, That 70's Show, Celebrity Deathmatch