That's the video of an attack drone not a surveillance one.
Check this source.
Initial probe results of IDF attack on three trucks to come out within days
www.jpost.com
They were following a Hamas militant, then they believed the guy may had got inside one of those trucks, they decided to murder everyone as a result.
Extremely poor and lax ROE which i guess Israel can always spin as "they were helping a terrorist" which would have probably worked if the people in the car were Muslims.
Claiming a bunch of Europeans and Australians are Hamas supporters is harder though.
I mean its not beyond the scope of the possibility, i mean the US bombed the crap out of a hospital in Afghanistan but the circumstances were different, they were responding to a firefight call, the plane was ancient and failed mid air and the people just decided to eyeball a target, which of course led to the unfortunate events, also the AC-130 was disciplined for it.