It initializes with a quiet whir, servo motors turning the barrel a quarter inch to the right so that it can track the approaching crowd. It has only been in service for a few weeks, and the only operations it has been required to perform so far have been ID checks and package scans. This will be different.
According to its own internal reference data, it is called the Vanguard. It is on the cutting edge of military engineering, and there is little else like it. Drums of flechette rounds rest in its innards-and a heavily armored camera lens peers out from its undercarriage, surveying the approach to the Governor's mansion-but these are merely features. They're not what makes the Vanguard special.
Any multimillion dollar defense company can make a gun that looks and shoots on its own.
This is the first time someone has made one that also thinks.
Comparing their facial expressions against an internal database, the Vanguard assesses the crowd and determines that a majority of them are angry. Many of them are carrying long, pointed poles, and it begins to cycle up its barrel before a context subroutine kicks in and identifies them as protestors. More internal referencing determines that the things they are carrying are signs.
Audio sensors begin to make temporary recordings of the noise of the crowd, paring away at the background static until they have clean, usable samples of the protestors' chants. They appear to be calling for the resignation of the Governor.
In order to prevent accidents or misunderstandings, the Vanguard has only one circumstance in which it will fire: when there is clear and present danger to the objective that it is protecting.
Recognizing that the sentry device may not always be able to sort out complex situations on its own, it is programmed to deliver fair warning to any approaching parties that are not cleared to pass its defensive perimeter. It does this now, initializing a program that covers spoken interaction with humans, and letting current flow to the speakers built into its base. "Please remain where you are. I will open fire if provoked."
It adjusts the gain a little, so that the words boom out over the crowd. The front line stops abruptly, wobbling a little as it collides with the line behind it. Protestors stare back at it, and it matches their expressions against its database. Defiance and confusion. "I have summoned an authorized morality technician to consult with me in order to determine whether you are a threat. Please do not move."
Angry muttering comes from the crowd. The Vanguard has been programmed to take charge of situations for this, and so it cycles its barrel for emphasis. This seems to cow several protestors, but a few of them step forward. One, a growing boy with acne scars and unwashed hair, looks directly at the turret. "He can't hide behind you. He has to answer to us eventually."
The Vanguard does not respond. It is aware that it has difficulty communicating with people, and so its default programming is to remain silent. Evidently, the boy decides that it must be bluffing and steps forward, forcing it to run its threat assessment routine again.
If it were to let the protesters past unchallenged, there is a very real possibility that they could do harm to the Governor or his estate. Therefore, they cannot be allowed to advance any further.
Stalling will work as a temporary solution, but the technician is already lagging by 0.5 minutes on his response time. The Vanguard quickly computes the chances that he may be otherwise occupied and determines the likelihood to be strong. Without a human authority to supersede its programming, it will have to work out a better deterrent on its own.
Calculating the odds that the crowd will do harm to the Governor, the Vanguard determines that—should the crowd advance by another two meters—there will be clear and present danger sufficient to necessitate an armed response. However, once the crowd has been thinned by 33%, it is unlikely to pose any further threat. Inflicting a death toll in excess of 33% would constitute unnecessary loss of life, a eventually that it has been programmed to do its utmost to prevent.
Cooling fans spin up, pouring hot air out through vents at the base of the turret. Kicking its processors into overdrive, the machine attempts to determine which protesters it is most allowed to kill.
It discards the mothers first. The ones marching with babies or swelling bellies. A PR subroutine insists that it should consider them last, and the Vanguard is obedient to its code.
The old men and woman are more of a problem. It decides that, on average, the old men are probably more acceptable targets. They tend to have a shorter life expectancy, and are unlikely to accomplish much in their remaining years. The old women, while they may live longer, also have a low likelyhood of contributing to society in their twilight years. Their knowledge and their personal stories may be valuable to their families, but weighed against the lives of younger, stronger people, this isn't worth much.
The next group that the Vanguard determines it will target is the people closest to the front. According to its database on human psychology, there is a high probability that firing into them first will cause the rest of the crowd to break. The boy with the acne scars is closest, and so his death will have the most dramatic effect on morale.
"I think you're bluffing." The boy steps forward again.
The Vanguard is not. It begins to initialize its firing routine. Idly, several subroutines begin to analyze the body that it is about to kill.
The boy is twelve years old. Possibly thirteen. Even going by facial topography and skin tone, his ethnicity is inconclusive. His features do, however, match a juvenile delinquency record, and so the Vanguard is able to put a name to his face.
Using the name, it digs into his background. Website access. Library fees. It determines that his mother is a chemist and his father is a historian, and that they have both been missing for several years. It discovers that they both had a background in activism, and—based on this—calculates a 56% chance that their child is now an orphan.
As the feeder belts rattle and the bullets begin their march towards the revolving barrel, the Vanguard extrapolates they boy's future. The most likely scenario is that, in the next five seconds, he is going to become a neutralized pile of leaking skin. In doing so, he will save those around him from the necessity of being gunned down as well.
Should he live, however...
Assuming he can survive the next couple of years, his life-expectancy jumps drastically. The boy is driven, and has a particular interest in the sciences. A good scholarship is not outside of his reach, and his psychological profiles indicate that he would do well at university.
Cross-referencing his academic records with his library check-outs indicates an early interest in biochemistry and pharmacology, something that—according to demographic data—the country sorely needs. Each day, fatal disease cuts away a tiny share of the working population, and debilitating illness does even worse; it keeps its victims in medical limbo, unable to meaningfully contribute, but reluctant to die. Their wasted knowledge and abilities, in turn, feed the nation's poverty problem, preventing it from digging itself out of the economic hole that it has crawled into, and worsening the endless cycle of protests and reprisals that is about to get the boy killed.
By killing him, the Vanguard's subroutines conclude, it will also be indirectly causing the death of thousands of unauthorized targets.
An emergency process spams itself into the Vanguard's task manager, temporarily interrupting its firing cycle. The spinning barrel whirls to a halt, and red maintenance lights switch on at various hardpoints on the Vanguard's chassis. The boy, who had been bringing his hands up to shield his face, is startled to find himself still among the living.
He stands perfectly still for a moment, as if waiting to see if the turret will change its mind, and then laughs out loud.
Of course it would never have shot him.
A formal inquest is launched—later, after the protestors have forced the Governor to flee by helicopter, and later still, after the military has reoccupied his manor—into why the Vanguard had failed. The diagnostic code that it spits back at the man tasked with assessing it clearly indicates that the machine had felt its operational abilities were compromised. In order to prevent it from continuing to act after internal diagnostics had found a fault in one of its target-assessment processes, the Vanguard had been programmed to assume an immediate safe-mode, pending maintenance.
It would have been worse, the designers had assumed, to have it mowing down invalid targets due to an unexpected glitch in its system than to have it fail to fire at all.
Several other high-profile incidents force them to admit that they were wrong.
A recall is issued later that year, and the Vanguard is scrapped for parts.