Difficulty: Easy
In mission 2-1 you'll face your first mutant dogs in a maze of shipping containers. When you exit this little maze you'll be greeted by a large Majini, who likes to punch. After taking this guy down you'll see a Majini on your left on a container. You should be able to hit the bomb in his left hand from a distance, while he struggles to hit you. Alternatively, if you have a rifle you could replay this level and pick him off a little easier, but it's far from difficult anyway.
Note: Don't get too close to the guy or Sheva might kill him and he'll also have a much better chance of hitting you