Canadian authorities confirmed on Wednesday afternoon that the soldier shot at the Ottawa war memorial died at the hospital, as the United States military put NORAD on “high alert posture” in response to the attack.

Multiple gunmen attacked the center of the Canadian capital on Wednesday morning, firing shots in the Canadian parliament as lawmakers were in session. One attacker is confirmed dead, shot by an off-duty security officer inside the parliament building. Thousands of government workers remain hunkered down in their offices, as police search for a second or third gunman.

The joint U.S.-Canadian North American Aerospace Defense Command (NORAD) was placed on a “higher alert status” early Wednesday afternoon, saying it is “ready to respond if needed.”