We need more info

Are the leaves opposite or alternate, toothed or smooth, lobed or entire. Are the leaves round, oval, long, egg shaped or heart shaped? Is the base of the leaf heart leaved, plain or does it have extensions unto the leaf stem? Do the leaves have petioles (little stems) or attached directly to the stem? Are the leaf veins netted or parallel? Are the leaves hairy? Is the stem hairy? Are there any thorns?

the leaves and trunk look like red alder

I'm not familiar with red alder, but your description of the tree, and its location being in PA, leads me to think of Autumn Olive. That tree was one of several shrubs heavily distributed by state agencies (none of which is taking any credit, now, for doing so) in the 50s and 60s; those plants are now taking over much pasture land in the sate. See http://www.ppws.vt.edu/scott/weed_id/elgum.htm for some info and pictures. If the plant is really Autumn Olive you do want to get rid of it, a difficult task. The trees sprouts readily from the stump and the fruit is loved by birds, which, of course, readily spread the seed. I have read that the fruit is quite delicious but I have never been able to get to tree and get some before the birds get to it. And at this point I'd rather be rid of the tree.