This photo shows the ladies' toilet signs in Sindang Station in central Seoul, Sept. 15. Yonhap

Police have arrested a 31-year-old subway station worker for killing a female colleague in the public restroom of a subway station in Seoul, one day before a court was set to sentence him on charges of stalking her.

The Seoul Metro employee, surnamed Jeon, allegedly stabbed the victim in her 20s to death in the ladies' restroom at Sindang Station on Line No. 2 on Wednesday evening. He was apprehended at the scene by other subway workers and ordinary citizens, and then handed over to police around 9 p.m.

After the stabbing, the victim called for help via an emergency bell in the restroom. She was taken to a hospital in a state of cardiac arrest but was pronounced dead 2 1/2 hours later.

Police said the suspect, wearing a disposable hair cap, lurked in the station for about 70 minutes before spotting, following and killing the victim.