OPK is everyone.
Telekill is one at a time but then he used super knife so probably like OPK with normal knife.
Is not the same
OPK (One Position Kill): You see all your enemy running in the same place. Is faster to kill.
Telekill: You Tele transport to an enemy when the previous is killed or pressing the keyboard arrows in some VIP hacks. Telekill is good because you can select and lock a player so you can kill everytime that enemy spawn.