How people become murderes?

To introduce the topic it is important to know what a murder is?

In simple words it is when a human being commits a crime of homicide. There are some reasons why people kill other people.

With some examples which I know I'll show you some reasons.

December 2006, Costa Rica.

Anais got divorce with his husband because she had a lover, one year later she got married again and this time it was with his lover,his name was Jose. She had have three children; a girl and two boys those with her last husband and with Jose she got pregnancy again, it was other boy. The first two year everything was good, but she started to repeat the story again, she had another lover, at the beggining Jose thought it was easy to figure out, but it was not for him. He started to drink a lot; and the murder instinct started to developed in him, he decide to stop this situation, he bought a delicious pizza and a poison, he wanted to kill Anais and the four children but it could not be like that, when Anais realized the situation; they started to discuss and this discussion became in a fight and he took a knife and he started to stab her body, he killed Anais in front of the children and later when Anais was alredy dead he took the poison and drunk it, he died too. As we can see the reason of this crime was the jealous. And every single day we see this kind of crimes and not only in our country, but around the world. Is for that reason that it is thought the mind get sick because the jealous.