Dylann Roof said he was not sure “what good it would do” to ask jurors for life in prison instead of execution, showing no remorse for killing nine black church members during a Bible study.

In his final argument to jurors, Roof, a 22-year-old white man, said he felt like he had to carry out the slayings on 17 June 2015.

“I still feel like I had to do it,” Roof said. Holding on to his racist beliefs, he said: “Anyone who hates anything in their mind has a good reason for it.”

Jurors will begin deliberations Tuesday afternoon and their decision must be unanimous. If they are unable to agree, a life sentence is automatically imposed.

Every juror looked directly at Roof as he spoke to them for about five minutes. A few nodded as he reminded them that they said during jury selection they could fairly weigh the factors about whether he should get life in prison or the death penalty. He noted only one of them had to disagree.

Roof said prosecutors showed hatred by seeking the death penalty against him.

Prosecutors said Roof deserved execution because he went to the historic Emanuel AME church in Charleston, South Carolina, with a gun and a “hateful heart”.

Assistant US attorney Jay Richardson said the 12 people Roof targeted were God-fearing church members who opened the door for a white stranger with a smile. Three people survived.

“They welcomed a 13th person that night ... with a kind word, a Bible, a handout and a chair,” Richardson said during his closing argument. “He had come with a hateful heart and a Glock .45.”

Najee Washington holds a photo of her grandmother Ethel Lance, one of the nine people killed in the shooting at Emanuel AME church. Photograph: David Goldman/AP

Richardson reminded jurors about each one of the victims and the bloody crime scene that Roof left behind in the church’s lower level. Roof sat with the Bible study group for about 45 minutes, and during the final prayer – when everyone’s eyes were closed – he started firing. He stood over some of the fallen victims, shooting them again as they lay on the floor, the prosecutor said.

The same jury that’s considering Roof’s fate convicted him last month of all 33 federal charges he faced, including hate crimes. Roof did not explain his actions to jurors, but in his FBI confession he said he hoped to bring back segregation or start a race war.

Nearly two dozen friends and relatives of the victims testified during the sentencing phase of the trial. They share cherished memories and opined about a future without a mother, father, sister or brother. They shed tears and their voices shook, but none of them said whether Roof should face the death penalty.

Richardson reviewed their testimony during final arguments and recalled Jennifer Pinckney’s remarks about her husband, Clementa, as he sang goofy songs and watched cartoons with their young daughters in his spare time. He was the church pastor and a state senator.

Roof acted as his own attorney and did not question any witnesses or put up any evidence.