Passage: Riel was the eldest of eleven children in a locally well-respected family. His father, who was of Franco-Ojibwa Métis descent, had gained prominence in this community by organizing a group that supported Guillaume Sayer, a Métis imprisoned for challenging the HBC's historical trade monopoly. Sayer's eventual release due to agitations by Louis Sr.'s group effectively ended the monopoly, and the name Riel was therefore well known in the Red River area. His mother was the daughter of Jean-Baptiste Lagimodière and Marie-Anne Gaboury, one of the earliest white families to settle in the Red River Settlement in 1812. The Riels were noted for their devout Catholicism and strong family ties.Riel was first educated by Roman Catholic priests at St. Boniface. At age 13 he came to the attention of Alexandre Taché, the Suffragan Bishop of St. Boniface, who was eagerly promoting the priesthood for talented young Métis. In 1858 Taché arranged for Riel to attend the Petit Séminaire of the Collège de Montréal, under the direction of the Sulpician order. Descriptions of him at the time indicate that he was a fine scholar of languages, science, and philosophy, but exhibited a frequent and unpredictable moodiness.Following news of his father's premature death in 1864, Riel lost interest in the priesthood and withdrew from the college in March 1865. For a time, he continued his studies as a day student in the convent of the Grey Nuns, but was soon asked to leave, following breaches of discipline. He remained in Montreal for over a year, living at the home of his aunt, Lucie Riel. Impoverished by the death of his father, Riel took employment as a law clerk in the Montreal office of Rodolphe Laflamme. During this time he was involved in a failed romance with a young woman named Marie–Julie Guernon. This progressed to the point of Riel having signed a contract of marriage, but his fiancée's family opposed her involvement with a Métis, and the engagement was soon broken. Compounding this disappointment, Riel found legal work...

Question: When did Riel decide he was leaving Canada?
early 1866