UPDATE: From a very reliable sounding account in the comments section:
I was walking to the Q and heard the crash, saw a sneaker go flying about twenty feet in the air. I was the first person there. A teenage girl was unconscious on the ground with a pretty severe head injury. She'd been knocked down by a woman driving a toyota camry who stopped immediately. The girl was jaywalking. I called 911, checked her pulse. She was breathing and had a steady pulse. Big crowd gathered around, including some of her friends/family members. She started waking up/trying to move and a couple of us held her to keep her in place. She may have had a broken arm/shoulder as well, but I was most concerned about the head/neck. It appeared that she had hit her head very hard on the pavement. Police came within about 5 minutes and took over the scene. The girl was conscious but clearly very badly injured when I left. No idea her name. I really hope she can pull through. It was horrifying. Please, please be careful crossing around that intersection.