Granted, the officers might have thought he did, and they didn’t get the full report from the 911 dispatcher, but here’s what they probably should have done.
Approach, figure out whatever direction Tamir would be most likely to hurt innnocent bystanders if he fired. Park maybe 20 feet away in that direction. Kill the engine, get on the loudspeaker and order Tamir to drop the weapon and put his hands up.
Given the reality of the situation, Tamir would have dropped the gun, put his hands up, and then the officers could yell at him a bit for waving the gun around and scaring people and all would be well.
And in the bizzarro world where Tamir was a threat, they’d be safe, they’d have protected innocent bystanders, and with a little distance they’d have time to possibly come up with a plan to bring him in alive.
Nearly running him over and opening fire before the door is even fully open should be reserved as a desperation move to take down someone ALREADY FIRING. That strategy removed the possibility of taking him alive, put the responding officers and anyone missed shots or richochets might hit at additional risk. This was an utter failure of an idea under these circumstances no matter how you look at it.
Those cops should be fired for incompetence. Then, if there was no evidence they were out to kill when they got the call, second degree murder charge, first degree if there was such evidence. They were incredibly reckless at best.