The third victim of the knife-wielding maniac who left a bloody trail across Manhattan in a broad-daylight stabbing spree Monday has died of her injuries as the brute confessed to the random killings, sources said. The 36-year-old woman — the alleged third and final victim of 51-year-old Ramon Rivera — succumbed to her injuries in the hospital Monday evening, police said. Rivera, a homeless man with an extensive criminal record and reported mental health ailments, allegedly confessed to the unprovoked stabbings that began in the morning and crossed the width of the borough from Chelsea to the East River, sources...