A nurse who admitted killing as many as 40 intensive-care patients with fatal injections this week was sentenced to life in prison without parole for 22 deaths in New Jersey.

Charles Cullen, 46, worked in nine hospitals and one nursing home – the Liberty Nursing Center in Allentown, PA — during his 16-year career. He was arrested Dec. 12, 2003. Notably, Liberty Nursing Center has told the Associated Press that it fired Cullen for “failure to follow company procedures.” Many of the hospitals have come under fire for allegedly not checking Cullen’s background thoroughly enough, or on the other end, not allowing others to be informed of his reasons for departure.

Cullen pleaded guilty in 2005 to hospital killings in New Jersey and Pennsylvania between 1988 and 2003. Prosecutors have accounted for 29 deaths.