A nurse working in a hospital in north England has been found guilty of murdering two patients and poisoning many others.

Victorino Chua, a 49-year-old father of two, was found guilty of killing 44-year-old Tracey Arden and 83-year-old Derek Weaver, both patients at Stepping Hill Hospital in Stockport, England, where Chua worked, by injecting insulin into saline bags, which were then inadvertently used by other nurses. The court heard that Chua also “changed tack” after police were alerted and began sabotaging prescription charts, increasing patients’ dosages. Chua was cleared in the death of a third patient, Arnold Lancaster.

The poisonings took place between June 2011 and January 2012, when Chua was first arrested, BBC reports. Chua was then rearrested in March 2014.

During the trial, the court was shown a letter found in Chua’s home in which the nurse wrote that he was “an angel turned into an evil person” and “there’s a devil in me.” Yet the prosecutor, Peter Wright QC, told the jury that the motive for the nurse’s actions was “impossible to fathom.” Chua now faces life in prison.

Get The Brief. Sign up to receive the top stories you need to know right now. Please enter a valid email address. Sign Up Now Check the box if you do not wish to receive promotional offers via email from TIME. You can unsubscribe at any time. By signing up you are agreeing to our Terms of Use and Privacy Policy . This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply. Thank you! For your security, we've sent a confirmation email to the address you entered. Click the link to confirm your subscription and begin receiving our newsletters. If you don't get the confirmation within 10 minutes, please check your spam folder.

Contact us at letters@time.com.