This is a photo of the blood of Ahmed Deeb, a 21-year-old unarmed protester who marched on the confiscatory "buffer zone" in Gaza. According to Suha Afyouni, Deeb has now died from the wound to his femoral artery. The Washington Post is also reporting a killing. Max Ajl has the story here.
Writes Eva Bartlett, of International Solidarity Movement, who took the photo (apparently the mass at right center is a stone):
Demo against the Israeli-imposed "buffer zone", April 28, Nahal Oz, eastern Gaza. [IDF] soldiers shoot one unarmed Palestinian demonstrator, Ahmed Deeb, 21. The bullet severs his femural artery, causing sudden and copious bleeding. Dr. Abdullah el Attar at Shifa hospital confirms that Ahmed’s injury is serious and that he has lost a lot of blood. Dr. Attar says the bullet used on Ahmed was a "dum dum", an exploding bullet which, on impact, breaks into many pieces. At the time of visiting Shifa Ahmed had been rushed to surgery. He is the 9th unarmed protester to be shot by the IOF ["Israeli Occupation Forces’] in less than 1 month, including the three shot last week, one of which was an international solidarity acitivist from Malta.
Update: Here is a video of the protest from B’tselem: