It doesn't look like poison sumac to me. More like a Sambucus. You might try to post it to the name that plant forum to get a species level ID, but you should be pretty safe.

Where is this plant growing? Poison Sumac grows on the edges of wetlands.

http://www.poison-ivy.org/poison-sumac

kimmq is kimmsr

Yes - definitely a Sambucus - Elder. If you look more closely you'll see it is shrub.