Peregrin Took
When Faramir returned unconscious, Denethor believed him to be fatally injured. That blow, coupled with a vision in the "palantír" of the forces arrayed against him, drove him insane. He ordered his servants to build a funeral pyre in the House of Stewards for him and his son. Denethor's temporary servant, the Hobbit Peregrin Took, went to alert Gandalf and Beregond, one of the Tower Guards he had befriended. Gandalf and Beregond stopped the impending sacrifice just in time. Mad with grief, Denethor jumped onto the lit pyre, burning himself alive.