Don't be confused by the title of the video, Israel Carnage Civilians.
The video was posted on Liveleak as an alleged video of Israel killing Gazan civilians. Naturally, the video did very well on reddit, until it was proven that the video is actually from 2005 and is actually video from September 2005 when a Hamas truck with explosives went off in the Jabalaya refugee camp.
On the reddit page, the following refutation was posted of the claim it was from the current war:
All in all, we should thank the person who posted the video, since it gives a fine illustration of the kind of people who were 'democratically' elected to govern Gaza.
THIS VIDEO IS MISLEADING
The video was not taken on January 1st 2009. It was not taken in a civilian market, and it was not the result of an IDF air strike.
This video is from September 23rd 2005, and was taken in the Jabalya refugee camp in the northern Gaza Strip. A Hamas pick-up truck carrying Qassam rockets detonated by mistake during a Hamas rally, leaving at least 15 killed and dozens more injured.
The pick-up truck in question is visible for a split-second at the start of the video. The section of the video showing the pick-up exploding has been edited out. The large number of Hamas personnel present, the number of injured in military uniform, the large number of civilians and Hamas flags all over the place confirm this.
Compare the video from 4:08-4:24 with this photograph taken after the blast at the rally. In the background of the video the man shown in the white top in this photo is clearly visible tending to one of the casualties. Another person is shown coming over to him and placing the distinctive purple/green striped blanket over the body laying next to him, and the wooden pole he is knelt next to is visible.
A side-by-side comparison of a frame from the video at ~4:08 and the aforementioned photo from the CBS News article is here.
News articles about the actual incident depicted in this video:
Palestinians killed in Gaza blast - At least 15 Palestinians have been killed and scores injured in a blast during a parade by the militant Hamas group in the Gaza Strip. A truck carrying gunmen and home-made weapons blew up during the rally in the Jabaliya refugee camp in northern Gaza.
Israel has denied involvement, while the ruling Palestinian Fatah faction said it held Hamas responsible. [...]
An unnamed witness was quoted by Reuters news agency as saying "I was thrown several metres, then I looked behind and I saw people dismembered and lying on the ground dead." [...]
— BBC News
Gaza: Blast during Hamas rally kills 19 - At least 19 Palestinians were killed and some 80 more were injured Friday from an explosion that occurred during a Hamas rally at the Jabalya refugee camp in north Gaza.
While the Palestinian Interior Ministry has reported that 19 people died in the blast, hospitals said that at least 10 people were killed. Some of those killed were Hamas members, and the rest were citizens, among them two children, who took part in the rally.
The Palestinian Interior ad National Security Ministry said that according to eyewitness accounts the blast occurred inside a vehicle carrying Qassam rockets and was not the result of IDF fire.
A videotape of the rally showed a jeep blowing up, followed by images of people running for safety. [...]