In Early September, 2472, three squadrons of unidentified Axels had emerged from San Franciso bay and moved their way east. They weren't discovered by the local authorities until 11:14pm local time, at which point a firefight erupted.
The UWs (Unidentified Walkers) were armed with a heavy autocannon that fired depleted uranium slugs at high velocity. Against KR-14As, they were particularly devastating. The units appeared to be unmarked, save for one lead unit which had a green notch on the head. It is said that witnesses reported a lead squadron of seven units stopped by a house to remove someone from the premises, but little is clear about this particular part of the incident. After the 'extraction' the units retreated to the coast and disappeared into the bay. It is thought that they were returning to a Submarine Axel Carrier, which had slipped into the bay undetected only that morning.
Little has been released or made clear about the incident. There was an attempted cover-up, but of course details leaked out about the story. Over the years more details cropped up- either by conspiracy theorists or from various attempts to rationalize the event by the US Government (and, by extension, the UEPC).
Apparently the units were an independent raider force, sent to take hostage the daughter of prominent politician. Apparently the coup was by a foreign power, and she was evidently returned after two days of fierce searching.
However, the official story does not match up with the facts. Following the event, the house was cleared and the family that lived there disappeared. It was never in the ownership of a leading diplomat, rather a mid-grade engineer in one of the local labs. While the local neighbors could confirm some details about the family that was there at the time, all the official records were purged from the event. Key witnesses also disappeared. Most of the 'confirmed facts' of the event come only from gossip that followed.
It would be decades before the units themselves would be identified: ER-114 Jogis. The Model C and D types appeared in the Astra catalog on the black market and it bears suspicious similarities to the unit reported to have partaken in the attack. The popular conspiracy theory is that the raid was funded and lead by one of the sons of the prominent and wealthy Errat family. Desiring to rescue the engineer's daughter from the 'prison' of her father's house, he funded the venture and lead the attack personally to extract her, willingly or not. Since then the units have not been publicly reported to have appeared though it is known bases all across the pacific suffer many raids from raiders and mercenaries operating Axels... this group may be one of them.
Based on data from the C and D models, the ER-114 model A was apparently an attempt by Astra to manufacture standard-grade Axels to put them on the market for cash. Performance-wise, the ER-114 is a little tougher than the KR-14s. While not as fast, it is a little more nimble and can carry a greater payload. It is thought that two things contributed to their victory that night in the bay area: The auotcannons they were carrying with super velocity rounds, and the radar-absorbing materials that comprised their outer armor plating. The units could only be detected on seismic sensors- even their reactor emissions were shielded. Within the UEPC, the ER-114 type is designated with a red flag since it is one of the few Pirate Axels that can defeat a KR-14 with little modification.