... we didn't even know that Slayer could travel the Dreamworld at the time. When he was shot in the dreamwoods by Perrin in The Shadow Rising he woke up in Emond's Field, like he was just an ordinary Dreamwalker. At the time I thought he was simply Luc who became Isam when he was in Tel'aran'rhiod.

The way Slayer's powers work in that book are bizarrely different from those he employs elsewhere.

We were supposed to have all the information we needed at the time, so it seems improbable that we are supposed to divine that the perpetrator was someone using powers that we did not even know he possessed until several books later. At the time, Slayer had not demonstrated the ability to enter the Dreamworld in the flesh, and therefore to travel using it.

Plus, Slayer always leaves the corpses behind.