Three Israeli teenagers who were abducted by Palestinian terrorists in Gush Etzion last month were shot at least 10 times with a silenced gun in what appeared to be premeditated killings, a U.S. official involved in the investigation said. The disclosure clashed with speculation by some Israeli and Palestinian commentators that the captors intended to take hostages for a prisoner exchange but panicked and shot them. One of the teens, 16-year-old Naftali Frenkel, also held American citizenship. Israeli police believe the killings led right-wing extremist Jews to kidnap and burn to death an Arab teen from east Jerusalem in revenge. Missing since hitchhiking home on June 12, the bodies of the Israeli teens were discovered on June 30. Israel has said Hamas terrorists carried out the attack. One of the three Israelis, Gil-ad Shaer, 16, telephoned police and said, "They've kidnapped me!" after he, Frenkel and 19-year-old Eyal Yifrah got into a car which investigators suspect was driven by a Hamas terrorist posing as a religious Jew. A second disguised terrorist sat in the front passenger seat. A U.S. official involved in the probe said the FBI, whose mandate includes Americans abducted abroad, received a recording of the distress call from Israel within days and sent it for audio analysis in the United States. Distorted, tinny reports heard on the tape after an Arabic-accented male voice shouts "Head down!" in response to Shaer's attempt to raise the alarm were found to be consistent with shots from a silenced firearm, the U.S. official said. "There were 10 gunshots," added the official, who spoke to Reuters on condition of anonymity. The use of a silencer led U.S. investigators to believe the captors planned to kill the three teenagers from the outset, the U.S. official said. Israeli officials declined to respond to the American account of the investigation, saying it was still ongoing. "We haven't even caught the kidnappers yet, so we're not going public with anything more now," said an official with the Shin Bet security agency, which is in charge of the case.