The death of Sgt. 1st Class Kevin M. Johnson, who was killed fighting with the 1st Battalion, 7th Marines in Samarra, Iraq, last week has renewed concerns about the Marines’ readiness in the fight against ISIS.

According to the Marine Corps Times, Johnson, 32, was killed by an ISIS bomb while on patrol in Samarran.

It wasn’t immediately clear how Johnson was killed.

The Times reported that a member of the 1/7 Marine Brigade in Samarrra was killed while conducting a counter-IED operation.

The Marine Corps said it was a non-combatant incident.

“We do not have a specific report on the type of explosive that killed Sgt. Johnson,” the Marines said in a statement.

“However, as part of our ongoing efforts to identify and prevent incidents where civilians are harmed, we are taking a proactive approach to minimize civilian casualties and minimize the potential for collateral damage.”

It was the second time in recent weeks that the Marines had been targeted.

Last month, a Marine Corps helicopter crashed in the town of Marawi, killing a soldier and seriously injuring another Marine.

The Marines were among the first to arrive to help the Philippine Army in Marawi after a large-scale ISIS assault on the city.