First - thanks to everybody for posting comments.
Second - two dominating questions of the posters.
1. How are you sure it was a terrorist?
2. How do you know it was a human being?
Let me start with answering question number 1.
I know it was a terrorist (or more neutral - a Fatah al Islam fighter) because, at the moment there are only Fatah al Islam militants left in the camp. The Lebanese army has laid siege of the camp for almost three months now. That means you can not walk in or out of the camp anymore.
True - until a couple of weeks ago around 3000 Palestinian civilians still lived in the camp (by then 27.000 had already fled, mostly to the nearby Badawi refugee camp).
But these last 3000 civilians left around three weeks ago. Really, some people who comment here should follow the news a little better.
The only 'civilians' who stayed behind were 60 people, mostly women, who are married to Fatah al Islam fighters or are in other ways family members of the militants.
So lets call these women 'civilians', although they stayed with the fighters voluntarily (I mean 29.940 other Palestinians left).
Aha! So there is a change, you might now claim, that the blown up person in the clip was an 'innocent woman'.
My answer: No, there isn't. If you know anything about Islam, you will probably by now realize that an Al-Qaeda style organisation would NEVER EVER use women as fighters. I mean - be real. Yes, over the last couple of years, there have been a couple of female suicide bombers. This is though still extremely rare and mostly used in case male suicide bombers don't have access to a certain targets. But women just do not participate in battle. This is, within the Al Qaeda mindset, entirely haram (sinful).
The 60 'civilians' in the camp, are hiding in basements and tunnels. Most of these shelters are build by the PLO in the '80s during the Lebanse civil war. But with mainstream Fatah (PLO) crumbling, Fatah al Islam took over the Nahr al Bared camp in or around January of this year. They are using these underground PLO bunkers to try to stay alive. Also Fatah al Islam fighters basically stay underground. The shelling by Lebanese forces is so extreme these days, that there is a very small chance of surviving in the open.
Fatah al Islam fighters though still occupy some buildings above ground. Mainly the ground- and first floors of a couple of flats around a destroyed mosque. They still have snipers actively targeting the outskirts of the camp. How I know this: Well, on Tuesday I had to hide a couple of times behind a concrete wall because a Fatah al Islam sniper was shooting at us.
This all said: There is no doubt that the person who flew through the air was a Fatah al Islam fighter. No doubt.
And why call them terrorists? Well, Fatah al Islam beheads innocent people. They kill civilians. A couple of days ago I visited a 25 year old Palestian guy who lived and worked in the Nahr al Bared camp as a watch salesman. He was shot in the head - without any reason - by Fatah al Islam militants, two weeks prior to the beginning of the trouble in the camp. This is what the militants would do pretty often. Just randomly kill someone to frighten the others. The 25-year old guy survived the bullet in his head and sits now like a vegetable in a hospital. He lost his memory, has basically no clue who or where he is. Thank you very little Fatah al Islam! His parents, who are Palestinians, told me: "These terrorists should all be killed - there is just no other way."
Luckily for Fatah al Islam and Al Qaeda, the West is packed with apologists. Westerners who have no clue what radical Islam really stands for and who have no idea what Al Qaeda's actions and ideology really means to its main victims: Normal, smart, peaceful and middle-of-the-road Muslims.
Anyway. I admit that there is a 0.000006 percent chance that the person depected in the clip wasn't a Fatah al Islam fighter but an innocent jogger who got lost in Beirut, ran 90 kilometers to Nahr al Bared, fought himself a way through the Lebanese army lines and then was hit by a mortar. Please, again, be real.
Answer on question 2: Well, the flying object in the clip was a human being and not a chair or so. First of all, take a look at the clip, especially when he falls back to earth you clearly can see arms, legs etc.
Secondly: I put the camera next to me on a concrete wall (the same that protects us from sniper fire). I was kind of babbling with civilians next to me and, with them, chekcing out the heavy shelling 600 meters away. For already an hour shells exploded every couple of seconds. The moment the mortar in the clip hit and the person was catapulted into the air, suddenly everybody on the balcony started to shout: "Look, look. My god, that is a person!" So actually from the position we were in, we could all see it pretty clearly with the naked eye.
Last thing: How is it possible that a human being is being thrown in the air and not instantly torn to pieces by the impact of the explosion?
I have no answer to this question. I guess that most people who get hit by a mortar indeed die on the spot and never take off into the air. This, as it seems to me, looks very much like a 'freak-accident'. Maybe out of 10 million people who die because of shelling, one gets thrown in the air like in the video.
That's why its such unique footage.
Still - everybody is free to believe what the clip is all about. I have though something to admit to people who doubt the whole clip. Actually, after the person in the video fell back to earth, he stood up, removed the dust from his jacket and said in fluent Norwegian: " Gud - Jeg kjenne leve!" ("God, I feel alive!"). We later had a drink with him in a nearby pub. And the strange thing was - He was actually Danish.