Church gunman Dylann Roof laughed after confessing to FBI

A man accused of killing nine worshippers at a church in South Carolina laughed and made gun motions as he recounted the attack in a videotaped confession, it has emerged.

Dylann Roof, 22, told the FBI he picked the historic black Emanuel African Methodist Episcopal Church in Charleston after learning online it was one of the oldest black churches in the South and because he did not think there would be any white people there.

In video footage shown at his death penalty trial on Friday, he explained that he wanted to leave at least one person alive to reveal what happened.

He told FBI agent Michael Stansbury that he wanted to kill black people because they rape white women daily.

"I knew that would be a place to get a small amount of black people in one area," he said.

"They're in church, they weren't criminals or anything."

The agent told him nine people had died in the attack on 17 June, 2015.

Roof replied: "There wasn't even that many people in there. Are you lying to me?"

When asked how he felt, he added: "Well, it makes me feel bad."

Testimony from survivor Felicia Sanders said Roof sat through the Bible study alongside pastor Clementa Pinckney and began shooting as the rest of the group of 12 closed their eyes for a final prayer.

In the confession, Roof said: "I was sitting there thinking about whether I should do it or not. That's why I say there for 15 minutes. I could have walked out."

Church surveillance videos indicate Roof was actually inside for 45 minutes.

Roof barely looked up as the confession was played in court. He told FBI agents questioning him that he could never look at the families of his victims.

The court heard he meticulously prepared for the shootings.

He carried eight magazines which could hold 13 bullets each, but only loaded 11 bullets so he could shoot 88 times - a number revered among white supremacists because it stands for Heil Hitler as H is the eighth letter of the alphabet.

In the video confession, Roof said he left bullets in the magazine to kill himself but changed his mind when he did not see any police.

Two handwritten notes were found in his car - one to his mother and one to his father.

Roof told the court in Charleston that the killing of unarmed black man Trayvon Martin in 2012 was a turning point in his life.