Monsturd (2003)

Escaped serial killer Jack Schmidt is on the run from the police and FBI after escaping from jail. They corner him and gun him down in a sewer tunnel, where he falls into a pool of chemicals dumped by the company who created it, Dutech. The combination of feces and this chemical transforms him into a half human, half feces creature, who goes on a killing rampage. And it's up to a group of local law enforcers to stop him.