According to the Bible, who was the first murderer?

In the biblical Book of Genesis, Cain and Abel are the first two sons of Adam and Eve. Cain, the firstborn, was a farmer, and his brother Abel was a shepherd.

According to the Book of Genesis, Cain is the first child of Eve, the first murderer, and the third human being to fall under a curse. According to Genesis 4:1–16, Cain treacherously murdered his brother Abel, lied about the murder to God, and as a result was cursed and marked for life. With the earth left cursed to drink Abel's blood, Cain was no longer able to farm the land. Cain is punished as a "fugitive and wanderer". He receives a mark from God, commonly referred to as the mark of Cain, representing God's promise to protect Cain from being murdered.