KABUL, Afghanistan (AP) — Three men wearing Afghan army uniforms and driving an Afghan army vehicle forced their way onto a U.S. base in eastern Afghanistan on Friday and opened fire, killing one civilian contractor and wounding other U.S. troops, U.S. defense officials said.

If the shooters do prove to be Afghan soldiers, it will be the second insider attack this year by Kabul’s forces against their international allies. The attack happened at midday, several hours before Defense Secretary Chuck Hagel arrived in Afghanistan for his first visit as Pentagon chief.