Acknowledging that it is still the time for mourning, Obama said that it is clear that the killer had "no trouble" getting a firearm, and the U.S. will ultimately have to "shift" how it thinks about gun violence.
"Let's be clear: At some point, we as a country will have to reckon with the fact that this type of mass violence does not happen in other advanced countries," Obama said.
A gunman shot and killed nine people Wednesday in Charleston, South Carolina. The suspected killer, identified as 21-year-old Dylann Storm Roof, was apprehended Thursday morning.
The Justice Department and the FBI opened a hate crime investigation into the attack by the white suspected gunman, Attorney General Loretta Lynch said Thursday.
The shooting took place at the Emanuel AME Church, Charleston Police Chief Greg Mullen said. He said there were survivors, but would not say how many, or how many were inside at the time of the shooting.
State Sen. Clementa Pinckney, the church's pastor, was one of the victims of the attack, sources told NBC News.
Mullen described the suspect as a white male in his early 20s. He said he believed it was a hate crime, but would not elaborate.
"The only reason that someone could walk into a church and shoot people praying is out of hate," said Charleston Mayor Joseph P. Riley. "It is the most dastardly act that one could possibly imagine, and we will bring that person to justice. ... This is one hateful person."
—NBC News and The Associated Press contributed to this report.