Did the police investigate? What did they say? How well was the fence maintained? What was he doing near the fence? Why did the fence fail? Were there any witnesses or, anyone actually with him? Were his injuries consistent with how they claim he died? Was the fence damaged in the corresponding area or, did it have DNA there? How did they rule it? A suspicious death, death by misadventure? Sorry to be blunt but, did he die straight away? Who were called first- ambulance or police?
It's impossible to speculate on such a short description. Even with all the facts, it might be difficult. Presumably, the authorities did investigate? I can understand why you worry it might be suspicious though. I suppose, lots of things are possible but, all our actions leave traces. The hope is the police did a thorough enough investigation at the time and that all the evidence they discovered was consistent with that cause of death.
I'm sorry for your loss though. It's a shock- whatever happened.