"Plymouth Township police lost a hero this evening," Ferman said during a news conference with township Police Chief Joseph Lawrence.
Ferman declined to identify the suspect or discuss details of the killing, which occurred in the area of Conshohocken and Ernest Station Roads, calling it an ongoing investigation.
"There are just no words that can begin to express the magnitude of this tragedy for Officer Fox, his family, his wife, and his beautiful little girl," Ferman said. "This was the day we prayed would never come."
Fox's police dog, Nick, also was shot but survived.
"This was a senseless, senseless act for a car accident," the police chief said.
Just after 10 p.m., about 50 officers lined the back entrance of Montgomery Hospital, lifting their arms in salute as Fox's body was loaded into a coroner's van.
An escort of about seven motorcycles, flags waving, sped off after the van.
Earlier, nearly two dozen of the slain officer's relatives, well-wishers, and fellow officers had gathered in the parking lot outside Montgomery Hospital in Norristown, exchanging hugs and sympathetic words.
At one point, a uniformed officer emerged in tears.
Cars from the Montgomery County Sheriff's Office and Plymouth police kept other onlookers at bay.
The news conference was held in a parking lot at the Montgomery County Fire Academy on Conshohocken Road, about a half-mile from where the shooting took place.
Earlier in the evening, police and fire police had blocked off all access to the area around the shooting, waving away all traffic for more than a mile around.
Elm Street in Conshohocken, approaching the shooting scene from the south, was blocked off, as was Ridge Pike from the north. Reporters were allowed to drive in a caravan to the fire academy about 8:30 p.m. All other traffic was kept out until at least 10 p.m.
"We lost an incredible human being tonight," Ferman said.
"When he volunteered to go back [to Iraq] the second time, he didn't even tell his family he volunteered. He was that kind of a man," Ferman said.
"Officer Fox had an extraordinarily bright future," Montgomery County Commissioner Josh Shapiro said. "His family should know the community is mourning with them."
Plymouth Township has nearly four dozen full-time officers, serving a community of 16,000, according to the township police website.
A Facebook memorial for Fox had more than 6,200 likes by 11:30 p.m.
A person named Dan Miller wrote on the page that he knew Fox.
"Brad always had a smile on his face and lit up a room when he walked in," Miller wrote.
"Plymouth Township lost a great cop, who just came in and did his job with the utmost professionalism on a daily basis. Don't think there is much more I can say about the guy. Oh, yeah, he was a hell of a hockey player too. RIP, Buddy!"
The last police officer from the Philadelphia suburbs to die in the line of duty was Officer Christopher Jones of Middletown Township, Bucks County, who was struck and killed after a traffic stop along Route 1 in January 2009.
Contact Jeremy Roebuck at 267-564-5218 or firstname.lastname@example.org, or follow @jeremyrroebuck on Twitter.
Contributing to this report were Inquirer staff writers Jeff Gammage, Dan Hardy, Jessica Parks, and Sam Wood.