I can only assume that the second half of the epitaph refers to the younger John Bulkley (b. 1749), who was indeed a member of Harvard's class of 1769. This makes sense — the second half clearly eulogizes a young man.
It's strange, though. The Park family would have known the Bulkleys, so perhaps this epitaph was not confusing to them, but it departs rather significantly from the usual pattern of epitaphs. If there is a verse or eulogy beneath the vital information, it is almost always dedicated to the principal honoree. I've never seen anything like this one before.
Col. John Bulkley and John Bulkley, Jr.
d. 1772 and 1774