The "Governor's Guards" of Dallas County had not organized at this time. I will checks later to see if Cussons appears on one of the early company rolls from the Army of Alabama.
Companies involved in the capture of Mount Vernon arsenal and Fort Morgan were all from Mobile. Col. Todd commanded the 1st AVM Regiment composed of eight AVC companies from that city. Here's an article from the New Orleans Bee, Jan. 8, 1861, on this topic --
The sudden stroke of policy in Alabama, the coup d’etat and coup de guerre, was quietly and effectively carried out in this wise. Acting under the Governor’s orders, at eleven o’clock on Thursday night, the following companies detailed for that service embarked on a steamer for Fort Morgan: the “Cadets”, Capt. Sands; the “Fusiliers”, Lieutenant Emrick commanding; the “Independent Rifles”, Capt. Stikes; and the “Artillery”, Capt. Ketchum. Steaming down the bay they arrived at the Fort about 3 o’clock, and quietly occupied it, its only garrison being an Ordnance Sergeant and his family, and a laborer or so. The Fort is now held by the greater portion of the force which took possession, about two hundred men being under arms. The works are being put in more defensible condition.
The detachment detailed for the seizure of Mount Vernon U. S. Arsenal, located forty-five miles up the river, consisted of the “Mobile Rifles”, Capt. Woodruff; the “Washington Light Infantry”, Capt. Gracie, and the “Gardes Lafayette”, Captain Belloc. They embarked about the same time as the detachment for Fort Morgan. They arrived at the Arsenal about daybreak, and being provided with ladders for the purpose, escaladed the walls of the premises at three different points simultaneously, and formed around the armory in the center. The garrison, consisting of a squad of about thirteen soldiers and as many Government employees, of course made no resistance, being captured before they knew of the presence of an enemy. Had they not been taken by surprise, however, and had they been so disposed, they might have given some trouble and shed some blood, as the arsenal is defensible against musketry and their number was more than a third of their assailants. The arsenal contains 20,000 stand of arms, 1500 barrels [not kegs] of powder, 300,000 rounds of cartridge, and other munitions. It is now held by thirty men of the “Washington Light Infantry”, who are having pleasant duty we suspect.