Read some of Massad Ayoob books on calibers and stopping powere.....
"A large guy tried to shoot a police officer on a routine traffic stop. The officer drew his 40S&W loaded with 135jhp and fired one shot. The bad guy dropped and was clinically dead 10 seconds after the shot. The corroner called the police department and asked what explosive charge was inserted into the bullet that was used". The 40S&W brings more to the table than a 9mm. That's not to say a 9mm isnt effective but big and fast is better than smaller and fast.
This doesn't impress me one bit. The same could happen with any caliber, even a .22 short.