Wheelchair-user Abu-Thurayya, 29, was shot in the head during anti-occupation demonstrations by the Gaza Strip perimeter fence, one of four Palestinian fatalities the same day.
"The initial investigation indicates that no moral or professional failures were identified," said the Israeli army statement, which claimed that "no live fire was aimed at [Abu Thurayya]" and that it was "impossible to determine" exactly "what caused his death".
The army statement additionally praised the "restraint" showed by the Israeli soldiers present at the time, in the face of a protest that threatened "the sovereignty of the State of Israel".
The military acknowledged the use of live ammunition against unarmed protesters, saying that "few controlled shootings were carried out towards main instigators", and that "troops received approval prior to shooting each round by a senior commander in the field".
Abu-Thurayya previously worked as a fisherman, but lost both his legs in an Israeli airstrike in 2008. He has since done a number of jobs and also regularly attended protests.
Ibrahim's mother said her son posed no threat: "He was only holding a flag, not an explosive belt or a bomb," adding: "I do not trust them or their investigations."