Police believe the suspect and victim knew each other and part of this physical altercation was caught on video. Crime scene investigators take careful inventory of the evidence left behind after teenage are is stabbed at the middle of the afternoon. The victim suffered life threatening injuries. Everything happen in the station, and once the individual realized he was stabbed he fled out, the end, to Center Street end of the station. And he fell down on the ground. Reporter the suspect, another teen, was long gone but investigators saw most of what happen on the Surveillance Video in the stee station. Apparently they knew each other a fight, off camera. The individual, the victim came off and view of the camera he lifted up his shirt and there was a pound there. Reporter police shot in search dogs but havent recovered a weapon. The t station was shut down for two hours and riders arrived to find the entire station surrounded in police tape buses were brought in to get commuters home.