SEPTA’s 28,000 surveillance cameras cover plenty of territory on a transportation network spread over five counties, but the electronic eyes can’t see everything.

As Tuesday’s mass shooting on a Brooklyn subway car shows, few security jobs are as tough as protecting public transit, wide open by its nature, from a determined lone-wolf attacker.

» READ MORE: Man arrested in Brooklyn subway attack charged with terror

In its wake, SEPTA officials sought to reassure the public they are doing everything they can, including with the extensive deployment of closed-circuit television cameras.

Transit police also immediately stepped up their presence with extra patrols from other law enforcement agencies, including the Philadelphia Police Department, Temple University Police, and the University of Pennsylvania’s police department.

“People have an understandable concern about their security,” SEPTA spokesperson Andrew Busch said.

The SEPTA cameras cover platforms and turnstiles in rail stations, as well as on board its entire fleet of buses, subway cars, and Regional Rail trains, he said. The Center City transit concourse is also under surveillance.

» READ MORE: What we know about the Brooklyn subway shooting and its connection to Philadelphia

About 2,000 of the cameras provide live feeds in stations on the Market-Frankford and Broad Street Lines and the Center City stations that offer connections to Regional Rail: Jefferson, Suburban, 30th Street, and Temple University, Busch said.

Images flow to SEPTA’s network-wide control center as well as to several transit police command centers, Busch said. Officers spot-check what’s going on, toggling between viewpoints, and can also focus on known trouble areas, he said. If there’s an incident, officers can quickly punch up the scene in real time.

“It’s not possible to fully observe all the camera angles at all times,” Busch said. SEPTA is in the process of hiring five retired law enforcement officers to help monitor camera live feeds, he said.

Video from cameras aboard transit vehicles is not live, but images can quickly be transmitted back to headquarters and distributed to law enforcement. When there’s a serious crime aboard a bus, train, or trolley, it’s taken out of service as soon as the operator can stop safely, per policy.

Each bus has from eight to 12 cameras aboard, depending on the vehicle’s size. Each train car has 10 to 12 cameras.

Images are stored on the cloud, and have often been helpful in making arrests. For instance, a suspect who raped a woman in a Macy’s restroom at 13th and Market Streets last year was caught near 52nd and Market Streets after uploaded video helped police track his flight from the scene.

SEPTA has 285 subway and rail stations and 2,800 transit vehicles; some Regional Rail systems, especially those farther from the city, do not have security cameras, Busch said.

The station cameras are supplied by Genetec Inc., based in Montreal, and are maintained by SEPTA’s communications and signals department.

Mobile cameras located on the bus, trolley, subway, and train fleets come from Gatekeeper Systems Inc., which also maintains them. The firm is based in Abbotsford, British Columbia, and lists a U.S. office in Bristol, Bucks County.