A public prayer vigil is planned for Sunday night around the corner from where four people, including the gunman, were shot to death Wednesday in Oakland. The candlelight vigil is scheduled for 6 p.m. at the boat landing off Messalonskee Lake, a short walk down the street from Wednesday night’s slayings at 41 Belgrade Road. Amy Derosby, 28, Amanda Bragg, 30, and Michael Muzerolle, 29, were shot to death by Herman Derico, 42, at the two-apartment house they all shared, police said.