To put it in short...
On Thursday, during the fans autograph signing session, Alonso got angry due to the constant pushing and hitting from the photographers. Also the photographers were making impossible for him to reach the fans and have some fun with them.
In the end, Alonso got mad when he saw one of the photographers standing over the wheel of one of the wheelchairs that can be seen on the picture. He reacted as you've seen (kudos to him), went inside the garage and, a few minutes later, when the media had gone away, he went out again to sign more autographs but in a more relaxed way.
Edit: I think I can find the full transcript of what Alonso said regarding this incident on Friday morning, but I would have to translate it to English. If anybody's interested, just ask.
On Thursday, during the fans autograph signing session, Alonso got angry due to the constant pushing and hitting from the photographers. Also the photographers were making impossible for him to reach the fans and have some fun with them.
In the end, Alonso got mad when he saw one of the photographers standing over the wheel of one of the wheelchairs that can be seen on the picture. He reacted as you've seen (kudos to him), went inside the garage and, a few minutes later, when the media had gone away, he went out again to sign more autographs but in a more relaxed way.
Edit: I think I can find the full transcript of what Alonso said regarding this incident on Friday morning, but I would have to translate it to English. If anybody's interested, just ask.
The photographers had first some time to get pictures. Then, they had to leave for the fans to enter. They didn't leave, and not just that, as you said, one even used the wheel of the wheelchair as a "stand". And that's when this moment took place.











