victorino chua penned what he called a ` bitter nurse confession ' in which he spelled out ` how an angel can turn to an evil person ' .
in 13 pages of rambling , broken handwritten english , the filipino nurse said he might ` explode ' at any time , adding : ` if i will be pushed , they gon na be sorry .
' chua is accused of killing three patients by contaminating their saline drips with insulin and deliberately poisoning 18 others at stepping hill hospital in stockport between 2011 and 2012 .