Maybe a Rosa acicularis close to the species cross? Just a guess, there are so many species I have never seen, but I do have acicularis with very similar leaves, similar stipule with the red stripe, and they have very long sepals, much like the photo. The shape of the hip is also very similar. And as for the bristles, it is known as the Prickly Wild Rose.
Mine have some hips, but are not close to maturation. Even though your photo shows a very deep coloration, the sepals still appear very green. Maybe the weather (or something) is causing some premature coloration? And how large is the overall shrub?