Shanaa had left the vehicle he was travelling in to film Israeli tanks when he was killed.
He captured footage showing a tank firing the shell that killed him.
Markings on the vehicle that Shanaa was travelling in were emblazoned with "press" and "tv" and his flak jacket was clearly marked.
The Reuters news agency has called for a full inquiry by Israel's government and military authorities into the death.
Alastair McDonald, the Reuters bureau chief in Israel and the Occupied Palestinian Territories, said: "We are asking the army to explain was that [shell] aimed at the position where Fadl was filming?
"Clearly our concern is to protect our journalists and to ensure that such tragic events are not repeated."
Human Rights Watch (HRW) expressed deep concern about the use of antipersonnel weapons such as flechette shells in areas where civilians such as journalists were present.
A spokesperson told Al Jazeera: "An independent investigation is urgently needed to determine whether these principles were violated."
The Israeli army has expressed "sorrow" over the death of Shanaa.
Major Avital Leibowitz, a spokeswoman for the Israeli military, told Al Jazeera: "You have to take into consideration that in a war zone when there is exchange of fire and journalists are hanging around those places, that sometimes as a result of these consequences journalists will be hit."
Advocacy groups have repeatedly sought to have flechettes banned on the ground that they kill indiscriminately.
Thousands of the darts are released in mid-air when a tank shell explodes and can spray out over hundreds of metres.
HRW said in 2003 that the Israeli army should cease using the shells in the Gaza Strip.
The group said their use in civilian areas contravenes global conventions because of their potential for harming civilians and their indiscriminate nature.
Israeli doctors and Palestinian human rights groups attempted to get the US-supplied weapons banned in Israel five years ago.
But Israel's supreme court of justice ruled that although the 1980 UN convention restricts the use of conventional weapons that cause excessive injury, it did not prohibit those with "sub-ammunition such as flechette shells".
B'tselem, the Palestinian information centre for human rights, says at least nine Palestinians were killed by flechettes between 2001 and 2003.
The group also says that the Israeli army used flechettes against Hezbollah in the 2006 Lebanon war.