Cheriton's Viper Incident

The Cheriton's Viper Incident, also known as the Parapet Incident, was a pair of minor engagements between the UNSC and the insurgent Arcadian Outriders, which was remembered because of the UNSC's massacre of more than 1,000 Arcadian civilians.

Background
The Cheriton's Viper was the name of a convoy escort purchased by a warlord on Arcadia following the Covenant's initial attack on the planet. It spent the next sixteen years patrolling the Procyon system, keeping out the worst of the pirates even as Arcadia descended further into lawlessness. When the Covenant returned in 2549, it escorted a flotilla of evacuation ships out of the system.

This flotilla wandered about the Human Sphere for another two years, where concerns over the UNSC's ability to win the war eventually led to the creation of the Outriders. They believed that humanity's best chances of survival laid in escaping into deep space, and simply putting as much distance from the Covenant as they could. Supplies were collected and stored, vital technical skills were studied and shared around, and at times they raided military warehouses for defensive arms.

Battle
In December 2551, while the refugee fleet stopped over in the Beta Comae Berenices system, the Cheriton's Viper sounded a distress signal. The UNSC Upon the Parapet, a Charon-class frigate, responded and approached the stricken ship to provide assistance. As it docked, it was attacked by a boarding party that overwhelmed its skeleton crew, capturing the frigate. After civilians had been moved into its hangar bay, the convoy and its new prize fled the area.

The Parapet managed to regroup with other Outrider vessels, and was preparing to depart the Human Sphere when they were intercepted in the Diadem system by the UNSC Feeling Lucky. A short battle ensured which ended with the Parapet disabled and boarded by the cruiser, who were under orders to recover the frigate intact. The presence of civilians made the subsequent ODST assault long and bloody. Eventually, the ship was recaptured and prisoners and civilians were offloaded onto the cruiser.

Although naval personnel were sent to repair the frigate, it was subsequently destroyed when nuclear scuttling charges planted by the Outriders detonated. In retribution, everyone taken from the Parapet were spaced out of the Feeling Lucky 's airlocks. What remained of the frigate was tagged for later salvage.

Aftermath
Following the Incident, the UNSC conducted an investigation that ultimately saw most of the involved personnel being demoted and transferred to Reach to carry out their probations. Though the whole affair was quietly buried and classified, an ODST nicknamed "Angel" leaked it to the public, and condemned the lack of justice that was dealt. Afterwards, a number of sailors and civilians in other compartments spread rumors of bodies tumbling past the viewports. A few even stated that they heard gunshots, though this was often disregarded, given that spacing would kill them anyway.

The event drove a wedge between the UNSC and various Outer Colonial populations. In the UNSC's case, they simply couldn't believe that there were still extremists that were willing to betray their trust and the loss of even a lowly frigate cost them a significant resource in their fight against the Covenant. However, it was later discovered that the captain of the Viper had worked alone: even his allies in the Outriders were shocked at what he did. Still, the fact that the massacre happened at all, coupled with the minor punishments dealt, reflected that the age-old belief that the UNSC cared little about the colonists.