Roger - "He" is actually a "she" in the nautical world! And "she" was in contact with a Booth -- Junius Brutus Booth, The Elder, to be exact. That is the name of the ship on which Booth's father was traveling when he took ill and died.
My original idea was to post an image of the steamer, but I couldn't find any, just that it sank in a hurricane in September 1855: http://www.thecajuns.com/lahurricanes.htm
The April 15, 1865, evening edition of a large-city American newspaper reported three deaths in one paragraph. One was President Abraham Lincoln. Who were the other two reported as dead?
Hmm... terse confirmation with little details and not mentioning William Seward's name. That makes me think the other person listed as killed was Fred Seward, along with his father.
On April 17, 1865, a Midwestern newspaper reported that John Wilkes Booth had been captured. What did the newspaper say had happened to Booth that led to his capture?