A woman was killed and a man was critically wounded Monday night when they stabbed each other after an argument on a CTA bus in the Washington Park neighborhood on the South Side, police said.

About 7:30 p.m., the 37-year-old man was arguing with 36-year-old Andrea Mays as they rode the bus in the first block of East 63rd Street, according to Chicago Police. Mays then pulled out a knife and stabbed the man in his right shoulder, police said.

After the wounded man got off the bus, Mays followed and another struggle ensued, police said. The man eventually took the knife from Mays and began stabbing her.

They were both taken to University of Chicago Medical Center, where Mays was pronounced dead and the man was listed in critical condition, police said.

Area Central detectives were investigating.