Considering how anti-gun most shows are these days, I thought that this ER episode was actually more balanced than most. They could have easily taken the easy way out. Think about it, it could of easily ended with a cop shooting the badguy and then giving a little speech bashing gun ownership. But no, it was an ordinary citizen with a concealed carry weapon that ended his killing spree. The cops and all of the victims were totally helpless during the entire rampage. The entire episode, police were running around like headless chickens while casualties kept coming in hand over fist. Both from gun shots and from getting run over.
Out of all the BS programs on TV today, like Boston Public, Titus etc, this ER season ender allows the audience make up their own mind. As the gunshot victims were coming in, it was also brought up by the gung ho male desk attendant that the killer also ran the cop over with his car. "Assult with a deadly weapon". While trying to get away, he hit a cop with his car and then dragged him down the street for about a 100 yards. Every bit as deadly as his pistol.
I think that the Killers gun was probably a .40 S&W, they never really mentioned the caliber but 12+1 is a common load for a .40. 9's are more like 15+1, or 17+1. The hero did stop the rampage using a 9mm, 5 shots to the torso.
I did applaud Dr. Mark Green's actions at the end, he let that M-F'er die on the gurney as he started to arrest.