Grasping for straws!

Been trying to get information about my ggrandfather John Shea who was married to a Johanna Costello  sometime in the 1840's.  John possibly emigrated to the US sometime before 1865 and sent for his children Patrick in 1865, Anastacia in 1867, and Margaret in 1869. His wife Johanna appeared in 1870 listed as a Widow,  I can find no record of John's death. I do find a John Shea  residing in Syracuse, NY in 1867 but not with his son Patrick.  There have been suggestions that John died while working on the railroad and was buried where he worked.  I cannot substantiate this but cannot find anything about his death.  Most frustrating!!  Any suggestions will be greatly appreciated.  Thank you.