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

The suspect, Deion Patterson, has been apprehended following an hourslong manhunt, Atlanta police said.

Police plan to hold a press briefing at 8:15 p.m.

Police in Cobb County said Deion Patterson was seen on video in the county around 12:30 p.m. ET, roughly 20 minutes after the shooting, though it's unclear if he's still in the area.

Cobb County Police Sgt. Wayne Delk said during a press briefing that after learning Patterson might be in the area, his team checked flock cameras and "did discover that the vehicle had entered Cobb County," located northwest of Midtown Atlanta, where the shooting occurred.

"Around 12:30 p.m., we did spot what appeared to be a suspect in this area, which is why we have such a heavy presence," Delk said.

Police did not discover the video footage until around 2:30 p.m., and Delk acknowledged it's unclear if Patterson is still in the county.

"He might still be in the area," he said.

The vehicle Patterson was believed to be driving was recovered by Atlanta police in a parking garage, Delk said.

-ABC News' Will McDuffie

Of the four women who were shot and injured in the medical facility waiting room, three of them are considered "critically ill" and are in the intensive care unit, according to Dr. Robert Jansen, the chief medical officer at Grady Health.

The most seriously injured patient remains in the operating room, Jansen said, while a second victim has completed an operation.

Another victim underwent an interventional radiology procedure, which is used to repair vascular injuries, and will need more procedures in the future, he said.

The fourth patient is considered stable, he said.

-ABC News' Darren Reynolds

Of the four people who were shot and injured, three are in critical condition and one is in the emergency department, according to hospital officials.

All four are adults, officials said.