CHICAGO (WLS) -- A man boarded a CTA Red Line train on the North Side after he was stabbed Tuesday morning, Chicago police said.The stabbing occurred at about 1:24 a.m. in the 7600-block of North Paulina Street. Investigators said the 54-year-old man was standing in the street in front of the Howard Red Line Station when someone came up to him and stabbed him in the chest.Police said the man got onto the Red Line train and rode a few stops over. He was found about two miles away at the Morse Red Line stop as someone saw him bleeding from his chest and called 911.The man was transported to St. Francis Hospital in critical condition, police said.CTA trains were bypassing the area while police investigated. Normal service was restored around 4 a.m.No one is in custody. Area North detectives are investigating.