Outside of the apartment window, there he was, lurking in the shadows. No pony knew of his existence. He was invisible in the night. He would decide to strike, when the time was right.
Song is woken up by a frantic pounding at her door. Looking at her clock, she sees that the time is 3:13 am. She races over to see who is at the door. As she opens the door, she sees a nurse.
"Oh, thank Celestia you're awake! You were the closest pony I could find!" She takes a minute to catch her breath. "By the way, my name is Nurse Redheart. I heard you are the new doctor, so I thought I would come here to get you and..."
"And?"
"I have a hurt pony outside. I sent another nurse to get a stretcher, she should be here in less than a minute. You have to come outside, please!"
Yes, that's right. No ambulance. Risky business.
"Uh, can't it wait until I finish sleeping?" Song thought she was finally going to be able to get a decent night's sleep in Ponyville. Good luck with that, doc.
"No!" Nurse Redheart says with a stern voice.
Without any further comments from Song, they run outside of the building. There, laying on the ground unconscious, is the aforementioned pony. There is a bloody bandage that was quickly wrapped around the pony's chest area.
"Oh, my." Song turns to the nurse. "Do you know what happened?"
"Well, it appears to be a stab wound, but I didn't see who did it. I was outside for a quick breather, and then I heard this awful, piercing scream. Uh, no pun intended."
How did I not hear that? Song wonders. "Who in Equestria would hurt another pony like this?"
"I...can't imagine."
In Equestria, it is unthinkable that somepony would injure another. Ponies are such gentle creatures, and highly unlikely to hurt even a fly. Maybe it wasn't even a pony who did this? But all the dangerous creatures nearby live in the Everfree Forest. They have never come out before without being provoked.
A pony with a stretcher quickly approaches them. "Here you go, Miss Redheart," she says.
"Thanks, now let's get this mare on the stretcher," Nurse Redheart orders.
Both nurses get the pony on the stretcher. All three of them wordlessly rush to the hospital.
They go into the ER, and there are only a few other nurses and doctors. This is most likely because nothing bad ever happens in Ponyville, at least not during the night. The only reason anypony is there at all is because of the patients that have to stay there overnight to recover.
They put the victim on a bed, and one of the nurses begin to unwrap the patient. Once the wrapping is off, the wound begins to ooze blood. Upon further inspection, it appears that a rib is protruding.
"Nurse Redheart, keep track of vitals. Nurse, um..."
"My name is First Aid. You may refer to me as Nurse Aid," says the quiet, white pony. Why is it that the nurses are always white mares?
"Oh, haha. You can administer local anesthesia, please. Just in case the patient wakes up."
"Right on it."
In Equestria, sterilization is unnecessary, because magic protects every living creature there from infection. Don't even get me started on how ponies contract diseases if they can't get infected. It's just too much to explain. I guess you could say that there are plenty of other things in the world that ponies can get ill from.
"Are we all ready now?"
"Ready!" say the nurses in unison.
"Okay then. We'll start by checking for internal bleeding and damage of any vital organs. Retractor, please."
First Aid hands her a retractor. Song uses it to open the wound a bit more to expose the underlying tissue. A rib is fractured, but that will heal on its own over time. The doctor then checks thoroughly to make sure no organs were pierced, which is actually quite difficult when there is blood everywhere. Doctor Song takes a rag and dabs the area inside the wound.
"It actually looks pretty good in there, guys. Needle."
Song is handed the needle. First, she removes the retractor, then swiftly sutures the wound.
"All's well that ends well, I suppose! Seriously though, couldn't you two have handled this on your own?"
"Well, I guess I panicked," admits Nurse Redheart. "I brought you here just in case. I was so scared that this pony got stabbed! How crazy is that?"
"Oh fine, I can go back to bed in a few minutes, anyway. After I wash my hooves off." Song then proceeds to wash her hooves, carefully walking to the sink on her back legs.
While at the sink, she asks, "Do either of you know her name?"
"Yeah, it's Rarity. She's going to be really annoying and whiny once she wakes up," replies Nurse Aid.
"Ugh, I'll be heading back home then. See you!"
With Song back in her bed, she tries to imagine the reason for somepony to want to stab Rarity, whoever she is. Wait, isn't she a friend of the new princess Twilight? That's not good. Maybe somepony was trying to rob her or something. Well, whatever it is, she is sure that some detective would get to the bottom of it somehow. There weren't really any clues left behind. It's possible that Rarity saw the pony's face, but it's not certain.