2. electrocution. 220 volts of conventional electricity, through a device similar to headphones, hit the pig's head. The reason why it is placed on the head instead of the heart is to let the current pass through the pig's brain and make the pig faint instantly. In the next time, the pigs will bleed to death immediately.
Step 3 shoot. It's not a traditional gun, it's a gun specially used to kill animals. Its power and penetration are relatively weak, but the bullets used are bullets from 9 mm rifles.