EbonStar Colonial Security Services is a large paramilitary organization responsible for the safety of 'colonial assets' for private colonies under corporate rule in the Far Arm. Judging by their widescale presence and equipment on Shear, a relatively new and small colony, it can be assumed EbonStar is a very heavily armed mercenary force, with dedicated operators and potent heavy weapons.
On Shear, they possess three different facilities, all of them in the desert area of the planet. A Barracks where the main detachment resides and operates the Quasar anti-artillery orbital defense cannons, an Armory fitted with an EMP cannon and a desperately constructed Wraith Trap meant to capture and study one of the few Wraiths EbonStar actually brought down.
From Bucket's report, the monsters 'overwhelmed colonial security forces within a week'. This is probably meant to imply the period when the monsters were openly attacking EbonStar and the colonists, as opposed to the months when they were simply building their strength on the colony, presumably slowly whittling away at the mercenary force on the frontier.
For all their firepower, it is quite easy to see how Shear's EbonStar detachment was overtaken so quickly. As Commander Park states on the Barracks map, they were better prepared to fight an orbital incursion from corp pirates or even a Sol Guard attack (as they quite clearly took Hub into account with the Quasar cannons), and a ground attack wasn't considered. The monsters not only came from overland, but they also fought EbonStar with tactics and abilities the mercenaries had no idea about.
Shear's detachment can be estimated to around a battalion at least (~300-800 soldiers) as an entire company was slaughtered on the Barracks map. They also used extensive robotic forces, from attack drones to sentry guns. Their small arms collection was average, the mainline weapon being the Gauss SMG and the Minigun for (presumably) heavy weapons troops.