When Joel escapes from the Fireflies and goes searching for Ellie in the hospital (roughly 29 minutes in) he shoots a person whose shape can be seen through a panel of frosted glass. If you pause you can clearly see that the bullet shatters most of the glass from the frame. The camera pans away and when it comes back a few seconds later 1/4 of the glass is back in the window frame.
Ellie's head changes position repeatedly between shots as Joel is carrying her unconscious body out of the hospital.
When Joel is on his rampage he takes a rifle, a Ruger Mini-14, belonging to one of the guards, and takes the spare magazines off another guard, who is carrying an M4 carbine, and inserts the M4 magazine into the Mini-14. While the Mini-14 and the M4 can both fire the same .223 Remington/5.56x45mm NATO round, they use different types of magazines. The Mini-14 uses a proprietary magazine design, with a different shape and locking mechanism than the magazines used by the M4/AR-15 platform, the two are not interchangeable. In real life Joel would have needed to unload the rounds from the M4 magazine and then load them into the Mini-14.