What Happened to William Killeen?

William Killeen was born at March township, Carleton Co., Ontario in 1832, the son of Denis Killeen and Mary Ahearn. He was baptized 7 Mar 1833 (Notre Dame, Ottawa), with John Lahey and Mary Kennedy serving as godparents.

In the 1851 census of March (Canada West [Ontario], Carleton County, March, p. 4), William is found in the household of his older brother Patrick, along with his widowed mother Mary and seven other unmarried siblings. Here his age is given as 19.
He is not found in the 1861 census of March, however, and he seems to disappear from the Canadian records. Two possibilities immediately suggest themselves (there are, of course, other possibilities, but these two strike me as most likely): 1. between 1851 and 1861 he died  at March township, and was buried without a headstone; or 2. between 1851 and 1861 he emigrated to the US.
In the 1871 US federal census of Virginia City, Storey County, Nevada, there is a J.W. Killeen, born in Canada about 1835, occupation “Keeps Saloon,” who is married to an Alice who was born in Ireland about 1840 (occupation “Keeps House”). Could this Nevada saloon keeper be the son of Denis Killeen and Mary Ahearn?