This is at best a one-sided characterization of this encounter. The "government forces" in this case had been engaged in unauthorized looting and attacks on Mormons in "Mormon counties."
They had taken prisoner three Mormons, and a report (or rumor) had gotten back to the Mormon capital that they were to be executed. The Mormon response was to launch a rescue attempt, which succeeded. Three Mormons died, and one of the militia.
Wildly exaggerated reports of massacre of militia by the Mormons at this "battle" was the main factor leading to the governor's "extermination order."
Yep, like I said, both sides were behaiving badly and each got the other fired up.
If Boggs hadn’t issued the order and brought things under control - real atrocities would have likely occurred.