He was a military engineer. He came from a prominent military and seigneurial family. His father, a seigneur, solider, and man of letters who was favored with colonial and imperial patronage, had established good connections with the elite of both linguistic groups in the colony, as well as with certain great English and French families. He would be criticized for his conspicuous desire to place his children's good jobs or good marriages; but their way of life necessarily depended on seigneurial revenues and above all on patronage and careers in the British empire.

He did not find himself without companions when he arrived. He met with his three brothers, Maurice-Roch, Francois-Louis and Charles-Michel, who often stayed at the Prince's London residence, sat in his personal box at concerts, benefited from his sponsorship, and gave ear to his counsel, all of which led them to venerate their benefactor. The Prince and Mme. de Saint-Laurent treated Edouard-Alphonse as if he was their son. They underwrote his fees for a private tutor and then paid 100 pounds a year for him to attend the Royal Military Academy in Woolwich (London). They provided him with new clothing, took him in for holidays, and gave him pocket money and presents such as money, a watch, and a gold chain, thus incurring a total expenditure of several hundreds of pounds sterling each year. In addition, at their table and at receptions and the theatre, Salaberry was in the company of many of the leading figures of the day, including the Duc d'Orleans and his brothers, the former Lieutenant Governor of Lower Canada, Sir Robert Shore Milnes, and his family, Major-General Frederick Augustus Wetherall, the Prince of Wales, and various Spanish and English generals and admirals.

He repaid his benefactors by applying himself to his studies, in which he did well, and by demonstrating to them his unfailing thanks. He gave evidence of a keen sense of duty as well as artlessness, humor, and warm-heartedness, in short an appealing blend of qualities complementing his physical transformation into a young man desired as tall, strong, and charming. Towards the end of 1809 he took five or six months training in surveying before he began his service as a military engineer. His education in a Protestant institution does not seem to have caused insurmountable problem.

The Napoleonic Wars took him to Spain, and during the night of April 6, 1812 he was struck down by a musket ball which participating on the assault on Badajoz with a division of light troops of the British army. The previous day he had had a premonition that great danger lay ahead for him. Lieutenant-Colonel Richard Fletcher, his commander, expressed the feelings of those who knew him: "He was universally esteemed by his brothers in arms, and all mourn his death." It was a tragic end for the most gifted, in intellect and character, of the Salaberry sons. Only Charles-Michel survived to perpetuate the name of their great family, Maurice-Roch died in India in 1809; his inconsolable parents had considered having Francois-Louis return home but he too died in India in 1811.