If there was a stampede, the only people who should be responsible are the people responsible for causing it.
Security at stuff like this is simply an illusion to make you feel safe, like the TSA. Ask yourself if a concert has several thousand people or more and there are only 100 unarmed guards, what are they really going to do if the entire crowd gets out of control? You can't plan your way out of people deciding to jump fences, stampede, and avoid reasonable barriers for crowd control. If the crowd gets out of control the only people who can reasonably handle that is a large anti-riot force.
Legally though, I'm sure the venue can be held responsible. But the only people at fault for people's death is the dumb-ass crowd.