Atlanta mass shooting updates: Victims identified

The suspected gunman, 24-year-old Deion Patterson, was armed with a semi-automatic handgun when he allegedly shot five people in a medical center waiting room, according to court documents.

The documents identify the surviving victims as Georgette Whitlow, Lisa Glynn, Jazzmin Daniel and Alesha Hollinger. All four of them remain hospitalized.

Hollinger was shot in the face, according to the documents, while Daniel was shot multiple times in the abdomen. Whitlow was shot in the arm and Glynn was shot in the abdomen.

Amy St. Pierre, 39, an employee of the Centers for Disease Control and Prevention, was killed in Wednesday's shooting.

Atlanta Mayor Andre Dickens released an impassioned letter addressed to city residents on Thursday pleading for change in the wake of Wednesday's mass shooting in a medical center waiting room.

"This suspect was arrested and will stand trial for his crimes," the mayor said. "But that doesn’t change the fact that one woman died, and four others were seriously injured. It doesn’t change the fact that our city experienced a collective trauma. Families are grieving today, and our community is on edge."

"We will learn more in the coming days about the circumstances of this shooting. But one thing we already know is that an incident like this is tragically too common in America," Dickens said. "We need national action to change the way we treat mental health. And we need action that keeps guns out of the hands of people who should not have them."

"We cannot accept mass shootings as normal in our country," he continued. "Other nations have challenges with mental health, but they don’t have this level of gun violence that we do."

"It’s the guns," the mayor stressed. "While we respect the rights conveyed by the 2nd Amendment, we also need more actions to protect the rights of our citizens to go about their lives -- to go to a doctor’s office, a supermarket, a gas station, their school -- without the threat of being gunned down."

The Centers for Disease Control and Prevention confirmed the 39-year-old victim who was killed in Wednesday's shooting as Amy St. Pierre.

"CDC is deeply saddened by the unexpected loss of a colleague killed today in the Midtown Atlanta shooting," it said in a statement. "Our hearts are with her family, friends and colleagues as they remember her and grieve this tragic loss."

-ABC News' Jason Volack

The suspect was taken into custody without incident, police said Wednesday during a press conference.

The suspect entered the medical facility shortly before noon and allegedly shot the first victim shortly after, Deputy Chief Charles Hampton said. The suspect spent two minutes in the building before exiting and going to a Shell gas station, where he commandeered a pickup truck, according to Hampton.

Officers were able to place the license plate number into the reader system, Hampton said, and received an alert at approximately 12:30 that the suspect was in Cobb County.

Technology "played a huge role," Cobb County Police Chief Stuart VanHoozer said, "but technology doesn't work without the dedicated people behind it."

Police had checked and cleared an unoccupied building they knew the suspect had gone into, VanHoozer said, adding that a "real-time operator" took a 911 call and had an instinct that it was legitimate, and they prioritized that call.

An undercover officer made the first contact with the suspect and had backup from uniformed officers, the chief said.

-ABC News' Darren Reynolds