The 15/16 year old pupil Alexandros Grigoripoulos was sitting with his friends at a coffee shop in Exarhia, central Athens. According to eye witnesses, a police car was driving by 'driving slowly and looking around, as they if were looking for something'. Eye witnesses report that the boys 'atacked them verbally', they exchanged angry words and some plastic water bottles were thrown. Reportedly a couple of plastic water bottles were thrown. The two policemen parked the car down the road and went back on foot. One of them threw a 'sound-light bomb' and the other shot the boy twice at the chest. A video by mobile phone on YouTube shows the two men walking away on their own.
It was then that people gathered around and the demonstrations and incidents began.
Initially the perpetrators claimed that they were cornered by 30 people and the shot was necessary for their safety. It is clear that this is not the case (even if it was, they should have driven on and called for reinforcement). Their defense lawyers quit for 'personal reasons' - it is reported that one of them quit because he did not agree with the 'defense line', or, more plainly put, because they lied to them about the facts.
Exarhia is an area where anarchist and left wing groups often hang out. It is also an area with coffee shops and bars frequented by young people, not necessary of the same political beliefs. From the events it is evident that these two policemen were driving deliberately by looking for trouble (police is not very popular in Greece, least of all among leftist groups), and they created trouble. Alexandros Grigoropoulos was not an anarchist, he was not involved in any left-wing group, and at the time was celebrating with his friends, not involved in any political activity (much less a violent one). He was the son of an upper middle class family residing in Palaio Psychiko, a suburb of Athens.
Here you can see the YouTube video, recorded by mobile phone from a nearby house: http://www.youtube.com/watch?v=jwJZHcMolUA