Why not give the orcs the built in line of sight behaviour and move the orc with a movement behaviour?
for each orc
orc has line of sight to player
system compare two values: distance(orc.x, orc.y, player.x, player.y)<200
-orc set orc.seesplayer : orc.seesplayer+1
-orc set bullet angle : angle(orc.x, orc.y, player.x, player.y)
orc has not line of sight to player
-orc set orc.seesplayer : orc.seesplayer-1
for each orc - orc set bullet speed: orc.seesplayer/10
set the bullet behaviour to bounce of solid and there you go!