Iran’s top nuclear scientist was assassinated on Friday, gunned down as he and his wife were headed to a resort town not far from the country’s capital of Tehran, and a top Iranian security official claims that the scientist’s killing was conducted by Israel using a remote-controlled machine gun hidden in a nearby car.

The semi-official news agency Fars was the first to report the alleged details of the attack, and on Monday Ali Shamkhani, secretary of the Supreme National Security Council, repeated the allegation at the funeral for Mohsen Fakhrizadeh.

The operation kicked off when the lead car in Fakhrizadeh’s security detail traveled ahead to inspect his destination, the report said.

At that point, a number of bullets were fired at Fakhrizadeh’s armored car, prompting him to exit the vehicle as he was apparently unaware that he was under attack, thinking that the sound was caused by an accident or some problem with the car, according to Fars news.

The outlet did not specify if those shots were fired from the remote-controlled machine gun or from a different source.

Once Fakhrizadeh exited the vehicle, the remote-controlled machine gun opened fire from roughly 150 meters (500 feet) away, striking him three times, twice in the side and once in his back, severing his spinal cord. Fakhrizadeh’s bodyguard was also hit by the gunfire. The attacking car, a Nissan, then exploded, the report said.

Fakhrizadeh was evacuated to a nearby hospital, where he was pronounced dead. His wife survived the attack, according to Iranian media.

A couple of caveats worth noting here. First, the original accoutns of Fakhrizadeh’s assassination didn’t mention anything about remote-controlled machine guns, but instead detailed an explosion happening first, with snipers opening fire on the scientist and his security team as they got out of their car to investigate the damage. The Times of Israel also says that several defense analysts doubt the Fars version of the story, pointing to photographs of the bullet-riddled armor car ,which they say “better fits the initial descriptions of armed, trained operatives conducting the raid” as opposed to a satellite-operated machine gun.

The technology certainly exists to control weaponry remotely, though whoever was responsible for the attack would still have needed human resources on the ground to assemble the machine gun, mount it in a vehicle, and ensure that there was enough ammunition loaded for a successful attack. Human assets would also likely have been on the ground as a backup in case the remote-controlled machine gun jammed or didn’t respond to commands, which further calls into question Iran’s version of events.

Regardless of how the assassination was pulled off, the death of the scientist in charge of Iran’s nuclear program is a blow to the country’s efforts to develop atomic weapons, and comes on the heels of several other successful efforts to sabotage the nuclear program.

Israel — long suspected of killing Iranian nuclear scientists over the last 10 years — has declined to comment on the attack on Fakhrizadeh, who founded Iran’s military nuclear program in the 2000s.

He headed Iran’s so-called AMAD program, which Israel and the West have claimed was a military operation looking at the feasibility of building a nuclear weapon.

Meanwhile, Iran’s Press TV reported Monday that the weapon used in the assassination Friday was made in Israel, according to Reuters.

“The weapons collected from the site of the terrorist act (where Fakhrizadeh was assassinated) bear the logo and specifications of the Israeli military industry,” an unnamed source told the English-language news outlet.

Israeli officials did not immediately respond to a request for comment by Reuters.

While Israeli officials are keeping quiet about the attack, the nation is preparing for possible retaliation, placing embassies on high alert and the Israeli Defense Forces issuing a statement saying that the military is maintaining “full preparedness against any expression of violence against us.”