Liverpool Mercury refers to the killing of Joseph and Hyrum Smith as an "assassination."
The Liverpool Mercury, and Lancashire General Advertiser 17, no. 1734 (August 2, 1844): 2
ASSASSINATION OF JOE SMITH, THE MORMON PROPHET, AND HIS BROTHER.
We have accounts from Warsaw, Illinois, of the assassination of Joe Smith, the leader of the Mormonites, and his brother, Hiram.
. . .
The Nauvoo Neighbor of the 2nd of July says, —“Thus perishes the hope of law; thus vanishes the plighted faith of the State; thus the blood of innocence stains the constituted authorities of the United States; and thus have two among the most noble martyrs since the slaughter of Abel, sealed the truth of their divine mission, by being shot by a mob for their religion!”