A gunman opened fire on Wednesday evening at a historic African-American church in downtown Charleston, South Carolina, killing nine people, including the pastor.

The suspect in the shooting is still at large. He was described as a 21-year-old white man wearing a sweatshirt, jeans and boots, Charleston police said in a message on Twitter.

"I do believe this was a hate crime," Charleston's police chief, Gregory Mullen, told reporters shortly before 1 a.m. ET.

"It is unfathomable that somebody in today's society would walk into a church when people are having a prayer meeting and take their lives," Mullen said.

APTOPIX Charleston Shooting

A man kneels across the street from where police gather outside the Emanuel AME Church. (Wade Spees/The Post And Courier via AP)

One shooting victim died at a local hospital, while the rest were pronounced dead at the Emanuel AME Church.

Charleston Mayor Joe Riley called it a "most unspeakable, heartbreaking tragedy," and officials promised to hunt down the suspect and bring him to justice. A reward for assisting in the suspect's capture was expected to be announced Thursday.

Police said the shooting occurred around 9 p.m. local time. There were survivors, officials said, but they did not yet have specific information on how many people survived.

State House Minority leader Todd Rutherford told The Associated Press that the church's pastor, state Sen. Clementa Pinckney, was among those killed.

Pinckney 41, was a married father of two who was elected to the state house at age 23, making him the youngest member of the House at the time.

"He never had anything bad to say about anybody, even when I thought he should," Rutherford, D-Columbia, said. "He was always out doing work either for his parishioners or his constituents. He touched everybody."

The website for the church said it has one of the largest and oldest black congregations in the region. It was built in 1891 and is considered a historically significant building, according to the National Park Service.

USA-SHOOTING/SOUTH CAROLINA

A small prayer circle forms nearby where police are responding to a shooting at the Emanuel AME Church. (Randall Hill/Reuters)

A bomb threat was later reported near the scene of the church shooting, but the threat was declared over before officials met with reporters.

A police chaplain was present at the scene of the shooting, and a helicopter with a searchlight hovered overhead as officers combed through the area.

A group of several men stood in a circle in front of a hotel near the church. "We pray for the families, they've got a long road ahead of them," Reverend James Johnson, a local civil rights activist, said during the impromptu prayer service.

Gov. Nikki Haley released a statement at 12:30 a.m. ET indicating that her family was praying for the victims and their families.

"While we do not yet know all of the details, we do know that we'll never understand what motivates anyone to enter one of our places of worship and take the life of another," Haley said. "Please join us in lifting up the victims and their families with our love and prayers."

Republican presidential candidate Jeb Bush, scheduled to make a campaign stop in Charleston on Thursday, cancelled that appearance given the tragedy.

"Governor Bush's thoughts and prayers are with the individuals and families affected by this tragedy," the statement said.

The city of 120,000 has already been dealing with racial strife, after an unarmed black man named Walter Scott was shot to death by police on April 4. The office who fired his gun, Michael Slager, was indicted for murder by a grand jury earlier this month.

Officials plan to brief the media again around 7 a.m. ET on Thursday morning.

Church shooting

The shooting on Wednesday night occurred at Emanuel African Methodist Episcopal Church in Charleston, S.C. (Google )

With files from CBC News and The Associated Press