South Korean police are investigating a 42-year-old man accused of setting his apartment on fire and stabbing neighbors trying to flee, killing five people and injuring 13 others.

The violence Wednesday in the city of Jinju shocked the nation. Prime Minister Lee Nak-yeon criticized police Thursday for what he saw as a failure to properly monitor a person known for past violence and clashes with neighbors.

City police say the suspect aggressively resisted arrest and has a history of mental illness. But they say he has not given a coherent statement on what happened Wednesday.