Just found Patrick Dwan's death record. He was killed in an industrial marine accident off of Long Island on April 1, 1918. The April 2 Brooklyn Daily Eagle has the story.
For others reading, Patrick was the 2nd child of James Dean and Susana McCluskey of PEI. Lena's nephew. Patrick (b. 1862 of James) had a cousin also Patrick Dawn (b. 1872, d. 1948, of James' brother Thomas, buried in St. Peter's Catholic Cemetery in St. Peter's Bay, King's County, PEI); both cousins had an uncle Patrick (James' and Thomas's brother, born 1845, as I recall), also on PEI. So it can be tough to sort out the Patricks:)