This is a species from the Brassicaceae and there are lots of these. Have you got a picture of the whole plant and of the leaves? And is it a wildflower or something from the garden? If it is a wildflower and if you took this picture near Vancouver, B. C. e. g. at a roadside it might be Hesperis matronalis which is very common in your area. But I mostly saw much lighter flowers of this species when I was there in early June.
