This is San Fermin in Pamplona. I was a regular there in my 20's. ( actually went there every year ). And running with the bulls is an awesome experience and usually not dangerous.
The bulls leave their compound at dawn and run through a maze of streets on their way to the Plazza where they will be "fought" in the afternoon.
While in a group you can actually run in the middle of them, with a bull on one side and a bull on the other...
Shet happens when some of the bulls slip and fall ( and it happens on that slippery round stones pavement ) and the bull stands up and has lost the group...and then it usually turns itself the other way round ( facing the pen it left minutes before ) and starts running back...against the horde of ( not bull runners ) bull followers ( a loose bunch composed of many young tourists and Hemingway wannabe's )...
And here they start dying and things like this photo start happening, quite a number of them every year..
But beyond that ( and US Rodeos also maim and kill ) this is a very serious, religious, mythical, occasion, at the very heart of our Iberian heritage.
This really is much more than can be surmised from this pix.