Leo told everybody to get away from that place. Right now they did not know the range of that Boss Monster and because of this, staying close to that place could be really dangerous for them.
Because of this, every fighter without wasting any more time began to go further away from the place. On the other hand, Leo already found the location of that monster. Most likely that Monster is able to use the sand control technique to travel through the sand.
Right now he could already see something approaching their direction while traveling through the sand. Naturally, he could feel the aura. Without he became sure that that is the Boss monster and fortunately every fight already backed away from that place.