Coyotito's scream is mistaken by the trackers as the cry of a coyote. One of them fires his rifle, and the bullet kills the innocent baby, whose name ironically resembles that of the animal that they thought he was.

Written as a parable, John Steinbeck's The Pearl alludes "The Parable of the Pearl," also known as "The Pearl of Great Price," found in the Gospel of Matthew in the New Testament of the Bible. In this parable, the instructive lesson is one in which the kingdom of heaven is depicted as a pearl of great value for which a merchant sells all that he owns in order to obtain it. 

In Steinbeck's parable, the lesson carries a meaning closer to the hymn that was written about "The Pearl of Great Price":

Have you given up all for this Treasure?
Have you counted past gains as but loss?
Has your trust in yourself and your merits
Come to naught before Christ and His cross?

Indeed, Kino and Juana initially are content in their humble life together, and their sense of family is strong although they are poor. However, they sacrifice all for the "treasure" of the pearl to purchase a cure the baby.

Initially, when their baby is bitten by a scorpion, the doctor refuses to respond to Kino, who is but a peasant. So, Kino seeks a great pearl in order to pay for the services of this doctor, who decides to attend to the baby only when he learns of the great pearl. While he is with Kino's family, the doctor tricks Kino into revealing where the pearl is hidden, and at night, he has someone come to steal it. That night Kino draws "first blood." 

This action is the beginning of Kino and Juana's troubles which end with their fleeing into the Sierra de la Giganta as they intend to go to Lorento to sell the pearl. Unfortunately, trackers soon discover their trail. Kino knows that he must kill these men before they kill him. So, he tries to sneak up on them. Just as he prepares to leap upon one of the men, his baby utters "a murmuring cry." The watcher listens, and then he stands, waking one of the men who is sleeping. This man asks, "What is it?"

"I don't know," said the watcher. "It sounded like a cry, almost like a human--like a baby."

The man who had been sleeping said, "You can't tell. Some coyote bitch with a litter. I've heard a coyote pup cry like a baby."

When the cry comes again, the one who has been watching says, "If it's a coyote, this will stop it," and he raises his gun. Kino leaps upon the man; however, the rifle goes off before he is able to strike his enemy. He kills the trackers, but not before his baby is shot. 

With their little son now dead, the hopes for his future and their happiness are dashed. Kino and Juana's life together is now a tragedy. Truly they have "given up all for this Treasure," the pearl. And, all has come "to naught" as in the hymn. 

Kino has found the biggest pearl he has ever found and he and Juana along with their son, Coyotito, head to the big city to sell the pearl. Kino realizes that there are trackers after them to get the pearl. Kino takes his family into the mountains and tries to hide from the trackers. Kino hides Juana and Coyotito in a cave and goes after the trackers. Kino fights them and kills one of them, after they had fired a gun shot towards the mountain. Without knowing it at the time, the bullet struck and killed Coyotito. Kino is too focused on attacking the trackers to realize what has happened. When it is all over Kino hears his wife's cries coming from the cave.

And then Kino stood uncertainly. Something was wrong, some signal was trying to get through to his brain. Tree frogs and cicadas were silent now. And then Kino's brain cleared from its red concentration and he knew the sound-the keening, moaning, rising hysterical cry from the little cave in the side of the stone mountain, the cry of death. 

This is such a tragic story, yet there is a real sense of family in the story, as well. Kino loves his family tremendously and he is trying to do the right thing for them. Unfortunately he loses his beloved son in the process.

This is a good question. Let me give you a little of the plot. Kino, along with his wife, Juana and son, Coyotito set out to the big city to sell the pearl. As they are on the way, they realize that there are trackers following them to steal the pearl.

Kino creates a temporary shelter for Juana and Coyotito in a cave. Kino goes down the mountain to mislead the trackers. Moreover, he waits for them. When the trackers are finally in sight. Kino plans his attack. However, right before he is about to attack, Coyotito lets out a cry and the trackers, alarmed, shoot in the direction of the cry. Kino eventually kills the trackers, but he later finds out that the shot actually hit his boy. Coyotito dies.

When he finds this out, devestated and disillusoined, Juana and Kino head back to town.