Another reason I think it's the Shadows who were behind the destruction of the jumpgate is that, in the B5 universe, it's considered a gross violation of rules of engagement to attack a jumpgate directly, because the jumpgate network is needed by
every spacefaring race. Not even terrorists would dare attack one.
The Shadows, OTOH, are so obsessed with chaos and disorder and death that there's NO law they would ever respect. They don't care how many people die, or how much destruction is caused. Indeed, that's their very reason for being - to cause as much chaos as possible. Destruction of jumpgates, whether or not there's anyone using them, is absolutely something they'd do.
Then again, terrorists are like that as well. They also don't care who dies, they also want to cause as much death and destruction as they can, and I doubt they'd respect rules of engagement any more than the Shadows would. So just forget it.
