long time reader has to subscribe to respond to this
OMG.. I'm with Felt. "Security Guards" shouldn't carry guns, and if they do there should be training and good sense that goes into using it. Shooting the suspects in the head is criminal.
WTFooey, if the guard didn't have a gun in this case, it sounds as though he might have been dead instead of the suspect. And it sounds as though some on this forum might have been happier with that outcome.
Now for important stuff: I'm not familiar with every state's law but can you provide a source showing that it is illegal to shoot someone in the head in a deadly force situation? Would it be better if he killed the suspect by shooting him in the chest? If someone is posing a deadly threat to you and you are justified in using deadly force, that force can include options such as running them over with your car. For example, you are in your car with no where to go but forward and the bad guy is in front of your car shooting at you. Gonna lay down and die or hit the gas?
Now I'm not some gun-toting nut (really not, otherwise I would be on a different forum

but I believe in the right to defend yourself. And to be given a fair trial before people like us on the internet decide that they are guilty based on a news report. The actions the security guard took can either be homicide or completely justified and this distinction can be a matter of actions happening one second instead of the next second. And hopefully the court (if this has to go to trial) will be able to recreate EXACTLY what happen so the justice will be done. But, at this point, only the security guard knows for sure whether he was justified. And the justification is based on what the guard knew at the time of the shooting. If for example, someone points a gun at you and says I'm going to kill you. So you shoot in self defense, you are justified (generally, based on the limited facts presented) even in the gun is unloaded (unless you knew the gun was unloaded ).
Personally, I hope the guard was justified. If not, I hope he is charged appropriately. But, currently, there is not enough publicly available information to come to a true conclusion as to his guilt or lack thereof.
Just to recap (no pun intended) maxmiles, if someone starts shooting at you, perhaps you can maintain your good sense to remember to aim carefully and shoot the bad guy in the chest instead of the head. But otherwise, do your job to the best of your ability, only use the minimum amount of force necessary, AND stay alive.