I'm trying to figure out what tree this is. This is in Massachusetts (USA), hardiness zone 6a [-10 to -5(F)]. It blooms white flowers.
I am going to guess Cornus kousa, Japanese Dogwood. The flowers aren't true flowers they are modified leaves akin to Poinsetta flowers. I am seeing the horizontal branching which is portrayed beautifully as 'layers' in a dogwood. The leaves look similar. Have you noticed little red 'fruit' looking things?
The other idea was Japanese Snow Bell. Styrax japonica. I feel badly that I am unable to see whether you've got opposite leaves, odd pinate...those buds remind me of this tree. Japanese Snowbell Styrax japonicus
It's a Euonymus. In the original photos, I didn't see the "wings" for E. alatus (burning bush), but the multi-stem form matches, as do the green buds. If the pictured shrub is 8 ft x 8 ft, then it could be the compactus cultivar (which would explain the missing wings): http://www.vivaipriola.it/wp-content/themes/x_lapriola/piante/cartimgs/EU05105_big.jpg
The added photos show more detail and confirm, to my mind, that it's E. alatus or relative like the Wahoo tree (as it's known here) - Euonymus europeaus (http://media.gettyimages.com/photos/euonymus-europaeus-picture-id697386211?s=170667a)
This species has highly showy fruits in the autumn, with colorful leaves (but not as colorful as burning bush); there are more than a few cultivars. Wahoo trees are most often tree-form rather than shrub form.