Video journalist Issam Abdallah died and six other journalists were wounded, one of them seriously, in strikes in the village of Alma Al-Shaab in southern Lebanon on 13 October.
"The initial findings of the investigation show that the reporters were not collateral victims of the shooting," the media watchdog Reporters Without Borders said (RSF).
"One of their vehicles, marked 'press', was targeted, and it was also clear that the group stationed next to it was journalists."
The journalists believe they were hit by fire coming from the Israeli side of the border.
"It is unlikely that the journalists were mistaken for combatants, especially as they were not hiding; in order to have a clear field of vision, they had been in the open for more than an hour, on the top of a hill."
The journalists' bullet-proof vests and the nearby vehicle were marked 'press'.
According to two journalists interviewed by the watchdog, an Israeli helicopter had flown over the scene a few seconds before the strikes.
Lebanese authorities have accused Israel of being behind the strikes.
The Israeli army said it was looking into the circumstance of the fatal strike.
The Israeli-Lebanese border has been rocked by violence since the war broke out in the Gaza Strip on 7 October, resulting in more than 8,000 deaths and 20,000 injuries, mostly civilians.