The killing last month of three Israeli teenagers was likely premeditated, and the terrorists who abducted them probably never intended to hold them hostage, a US official involved in an FBI investigation of the case said.

The official pointed to 10 silenced gunshots fired at the teenagers that were heard in an audio recording of the incident to support this assertion, Reuters reported Wednesday. Investigators gleaned the information about the shots from the recording of an emergency call to police from Gil-ad Shaar, one of the victims, minutes after the abduction.

During the call, Shaar whispered, “They’ve kidnapped me.” The emergency call center mistakenly thought the 2:09 minute call was a prank and did not act on it for hours.

The FBI is in the midst of its own independent probe, since one of the slain yeshiva students, Naftali Fraenkel, 16, was a US citizen. The US team received the recording for audio analysis days after the teens disappeared.

Israel maintains that Hamas is behind the June 12 abduction and killing of the three in the West Bank, and some Israeli officials have said that the operatives intended to use them as bargaining chips in exchange for Israeli prisoners held in Israel. But the US finding has the foreign investigators questioning whether the killing was ever intended to be a kidnapping.

The report cited a Shin Bet security service official declining to comment on the findings and its implications.

“We haven’t even caught the kidnappers yet, so we’re not going public with anything more now,” he said.

Fraenkel and Sha’ar, both 16, and 19-year-old Eyal Yifrach were last seen on June 12 at a West Bank hitchhiking post. Their bodies were recovered 18 days later in Halhul, near Hebron, after the IDF launched a massive crackdown on Hamas in the area.

Israel believes Hamas operatives Amer Abu Aysha and Marwan Kawasme, who have been missing from their homes since the incident, are behind the attacks, but the two have yet to be apprehended and Hamas has denied involvement.