There were no immediate reports of casualties. Throughout the summer, incidents like the rocket attacks have plagued military installations in Iraq.
Bolton's abrupt firing came after reports that he vocally disagreed with Trump's plan to host the Taliban for peace negotiations at Camp David.
The witness said he had heard the phrase during unit training before SEAL Team 7 Alpha Platoon deployed to Mosul, Iraq, in 2017.
The Trump administration has rejected suggestions it's moving toward war after deploying military assets in response to unspecified threats.