COLLEGE PARK -- A volunteer leading a prayer service at a Georgia megachurch was shot and killed Wednesday morning, and a former church employee was taken into custody at a shopping mall hours later.

The shots were fired just before 10 a.m. inside a chapel on the campus of World Changers Church International, which says it has 30,000 followers in College Park, a suburb south of Atlanta.

The church's well-known founder and leader, the Rev. Creflo Dollar, was not at the church at the time of the shooting, Fulton County Police Cpl. Kay Lester said.

Authorities identified the suspect as Floyd Palmer, a former facilities maintenance employee at the church in his early 50s. Lester said Palmer had resigned from his job at the church in August for "personal reasons."

Palmer was taken into custody without incident a few hours later at an upscale mall in Atlanta's Buckhead neighbourhood, Lester said. Police spotted his car in the parking lot. They didn't recover a weapon.

He was charged with homicide and possession of firearms in commission of a homicide, with additional charges pending.

About 20 to 25 people were gathered in the chapel Wednesday morning, when authorities say the gunman walked in and began shooting. No other people were wounded and the gunman fled in a black Subaru station wagon with tinted windows.

"He walked in calmly, opened fire, and left as calmly," Lester said.

The victim was identified as Gregory McDowell, a 39-year-old church volunteer who was leading a prayer at the time. Investigators were working to determine if Palmer and McDowell knew each other.

"We do not know if the victim was targeted," Lester said. "We are looking into that as he was the only person that was shot."

Ken Terry, a pastor at the church who is acting as a spokesman for McDowell's family, said the church family was distraught and trying to comfort McDowell's family.

"He would be considered a model dad," Terry told reporters. "To have this happen is just devastating."

Although the campus has security officers and surveillance cameras, Lester said the suspect was known to some of those at Wednesday's morning service, so his presence wouldn't have been unusual.

The 50-year-old Dollar is one of the most well-known African-American preachers based around Atlanta, with a ministry of satellite churches across the U.S.