Jerusalem ? An American peace activist volunteering as a human shield in the West Bank was seriously wounded on Saturday when Israeli troops allegedly opened fire on him.

Brian Avery, 24, from Albuquerque, N.M., heard shots fired and came out of his apartment building in Jenin to investigate just as an armored personnel carrier rounded a corner, said Tobias Karlsson, a fellow activist from Sweden.

Avery and Karlsson are members of the Palestinian-backed group International Solidarity Movement. Members of the group often insert themselves between Palestinians and Israeli soldiers to try to stop Israeli military operations.

“We had our hands up and we were wearing vests that clearly identified us as international workers when they began firing,” Karlsson said. “Brian was shot in the face, and it looks like he was hit by a heavy caliber bullet because of the extent of the wound.”

Avery was taken to a Jenin hospital but was transferred to an Israeli hospital. Karlsson said Avery was semiconscious when taken in the ambulance.

The army said homemade firebombs were reportedly being thrown at troops and it returned fire at gunmen in the area, although it was not aware of hitting anyone. An officer said that Palestinians were also shooting, and it was unclear whose bullet hit Avery.

The U.S. State Department said it was looking into the report.

“The U.S. Embassy in Tel Aviv and our Jerusalem consulate are now following up to find out what happened as well as confirm the identity and determine the welfare of the individual,” State Department spokesman Lou Fintor said in a statement in Washington.

Karlsson said he, Avery and a Palestinian medical worker not with the group were approached slowly by the troops and stood with their hands up for about 10 minutes. There was no communication with the soldiers, who Karlsson says fired unprovoked.