i'd released the legendary dogs, but didn't really know anything about them. Much later i was trying to catch new pokemon in a low level area right after the first gym's city and happened to come across raikou. I was really confused about why he was a level 40 in such an early area, plus he was big and scary-looking. Fortunately, i since i was catching pokemon anyway, my first pokemon knew hypnosis, so i put it to sleep and caught it on my first try!
liar. No matter what the legendary dogs run away except for mean look and block. If there asleep, they will still run away