This rider takes peace from the earth and causes people to kill one another.
And when he had opened the second seal, I heard the second beast say, Come and see. And there went out another horse [that was] red: and [power] was given to him that sat thereon to take peace from the earth, and that they should kill one another: and there was given unto him a great sword. (Revelation 6:3-4)
The Apostle Paul talks about Jesus coming as a thief in the night. Just prior to that people will be saying “peace and safety” and the sudden destruction will come.
But of the times and the seasons, brethren, ye have no need that I write unto you. For yourselves know perfectly that the day of the Lord so cometh as a thief in the night. For when they shall say, Peace and safety; then sudden destruction cometh upon them, as travail upon a woman with child; and they shall not escape. (1 Thessalonians 5:1-3)