Five passengers were shot while riding a Chicago Transit Authority bus on the city's South Side on Thursday, authorities said.

Two teenage boys and one girl were transported in critical condition to Advocate Christ Medical Center in Oak Lawn, said fire department spokesman Larry Langford.

Another girl was transported in good condition to Little Company of Mary Hospitals in Evergreen Park, Langford said. A fifth passenger was also transported to the hospital, but that rider's condition was unknown.

The shooting took place around 3:15 p.m. on a No. 103 bus, said CTA spokeswoman Wanda Taylor.

"A lone, armed offender boarded the bus and shortly after boarding the bus fired multiple shots," Assistant Deputy Superintendent Eugene Williams said at a news conference.

The male suspect exited the bus and ran south after the shooting, said Williams, who asked the public to call in with tips.

The driver quickly pulled the bus over to a spot she believed was safe, said CTA spokeswoman Sheila Gregory.