The officials initially believed that the two foreigners were US soldiers involved in the maneuvers. It turned out, however, that the duo were tourists.
Reports said the two, identified as Brian Thomas Smith, a British national, and Sigfried Whitman, a Dutch citizen, rented motorbikes in Angeles City.
They, however, later decided to just walk to the foot of Mt. Pinatubo due to the rugged terrain.
Upon reaching Porac River, unidentified men fired at the two tourists, killing Smith on the spot. Although wounded, Whitman managed to run away, said Senior Superintendent Ismael Rafanan, provincial police director.
He had been in contact with a search team composed of Air Force, Army and police personnel by sending text messages from his cell phone.
"He is saving on his cell phone battery so he communicates only through text messages. He said he was already feeling weak," Rafanan said.
At press time, a US military helicopter, with night-vision capability, flew from Clark Field to rescue Whitman who was said to be in the vicinity of Basa Air Base in Floridablanca town.
Following news about the incident, Maj. Allan Ballesteros, spokesman of the 600th Air Base Wing here, said US military officials immediately conducted a headcount of their men, but none was missing.