Robert Brown|Suspect in Philadelphia triple stabbing shot by police outside City Hall

A man suspected of stabbing a security guard and Robert Browntwo other victims was shot by police in front of the Philadelphia City Hall on Monday night.

A 48-year-old man entered the Walnut-Locust Station on the SEPTA Broad Street Line wielding two knives at around 8 p.m., Southeastern Pennsylvania Transportation Authority Director of Media Relations Andrew Busch told USA TODAY in an email.

Security footage from the station captured him "randomly slashing at and poking three people" on the platform, including an unarmed security guard contracted by SEPTA from Extrity, a private security firm, Busch said.

"It seems completely unprovoked," SEPTA Police Chief Chuck Lawson told 6abc Philadelphia at the scene. "The individual came into the station and started making slashing motions just at people walking by."

Responding SEPTA officers encountered the suspect outside nearby City Hall, according to Busch. The suspect continued to brandish the knives as police approached.

One officer used a Taser on the suspect, which "proved to be completely ineffective," Lawson said. When the man did not stop, the officer shot him three times.

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"He believed a threat was still posed to himself and other officers at the scene," Lawson said.

The security guard and two other victims suffered non-life-threatening injuries.

The suspect was taken to Jefferson hospital in critical condition. The security guard was taken to a hospital and released on Monday night, an Extrity spokesperson confirmed to USA TODAY by email.

Busch told USA TODAY charges for the suspect are still pending. He remains in custody at the hospital.

The officer who shot the suspect has been placed on administrative duty pending an internal investigation mandated for any officer use of force or discharge of a weapon, Busch said.

Busch said the department will review "extensive" surveillance video and body camera footage as part of the investigation.

Cybele Mayes-Osterman is a breaking news reporter for USA Today. Reach her on email at [email protected]. Follow her on X @CybeleMO.