"We have received reports that a mental patient has escaped from Lincoln State hospital. He is considered extremely dangerous, I repeat, do not try and approach any suspicious persons but rather alert your local authorities immediately. The mental patient is Neokalus Burr, he is 38, approximately 6'4", 240 pounds, armed and dangerous. Catching Burr is a top priority. Please contact the Sheriff's Department if you have any information about his current whereabouts. God bless, and stay safe."- Radio warning
He's a towering hulk of a man in a red boiler suit, black gloves, wears a pink clown mask, and uses a kitchen knife to kill people. According to radio transmission, he's 38 years old, approximately 6'4" (195 cm) tall, and weighs 240 lbs (108 kg).
He's an escapee of Lincoln State Sanitarium, and invades the home Sarah is babysitting at. He kills Jack with a screwdriver before moving in on Sarah. Sarah manages to gun him down with a revolver, but by the time the authorities arrive, his "corpse" is long gone.
In Sanitarium Massacre, the lore has Burr gunned down by police in a home invasion and locked up in a mental hospital for 8 solid years, before snapping, escaping his cell, and wreaking havoc upon the staff with his trusty handy dandy soulmate-ish butcher's knife. It's very possible that this game serves as a prequel to Babysitter Bloodbath, and that Burr preyed upon Sarah after finishing up the massacre of his hospital.