Peter is a blue-fleshed zombie, with -- like David -- only one eye. He wears a tattered shirt and pants; his chest is exposed. His jaw and stomach region seem to be scarred. When attacked by the chest, it disturbs the parasitic worm causing havoc in his internal organs. It's speculated that the parasite stays dormant until it feels agitated, proven by Peter's behaviour. If not attack by the chest, it will attack through other convetional means like his undead brethren.
Whenever shot in the chest, Peter writhes in pain, dies, and a parasitic worm bursts out; it latches onto players for a bite (like Murrer) but dies in one shot. Peter dies instantly with a headshot.