I never kept yellow labs, but I have kept other african Cichlids, yes its normal. He may well continue to do it, and if one fish show the slightest sign of weakness, watch out. My exp with africans is that they need a ton of room, or somebody is gonna die!
I got sick to death of moving the decor (didn't work) taking out the aggro one (next in line took his place) remove the target fish, (he picked the next weakest one). This was nearly 20 years ago, but I tried 3-4 different species of Malawi or Tanganykas, and had more frustration than enjoyment.
Kept peaceful fish ever since. Sorry, JME.