CHICAGO (WBBM)  -- Authorities are looking for at least two men who are considered armed and dangerous - and are believed to be responsible for a string of armed robberies and carjackings in the south suburbs over the past week - the most recent: today.

Riverdale. Calumet Park. And now Alsip: the latest place where armed robbers and carjackers have struck.

Alsip Mayor Patrick Kitching says the men robbed a woman who is a tollway employee outside her apartment in Alsip - then took her car.

Mayor Kitching says a short time later, Alsip police noticed the car and started a chase which led north up I-57.

And Kitching says the robbers left I-57, hit a pedestrian near 99th and Halsted in Chicago, then kept going.

"The car they're looking for is in the city somewhere. And we fully expect that they'll probably hijack another car so that they can change vehicles again. Whoever this is has no regard for human life whatsoever. Everything they're doing, they're pulling guns out."

Mayor Kitching says the pedestrian who was hit did not receive life-threatening injuries.