“But I don’t want anyone dying in my place when there was no chance he could survive. “
Where do you keep getting this “no chance to survive” baloney. Nobody expects a cop to jump off the Brooklyn Bridge because you are drowning. But outshooting this guy isn’t rocket science. He was a drug addled teenager who is in his very first shootout, watching kids fall, distracted by screaming, by fire alarms, half deaf from his own muzzle blast. There are far better than even odds that a good adult man with normal training can dump him without him even seeing it coming.
The cop is under no legal obligation to go after the gunman although still in many departments the culture would compel him to do so.
Not sure if there is a 'Good Samaritan' law in Florida that would protect the cop if a stray round he fired struck someone other than the gunman.