He studied at the Royal Military College in Kingston from 9 September 1880 until 1884, cadet number 106.
He also studied at the Royal Arsenal at Woolwich.
Hearn became a real estate agent and also administered the property accumulated by his father.
In 1890, he married Katherine M.
Ryan.
He served on the Quebec municipal council and was president of the finance committee from 1896 to 1898.