Waltham - Mr. Walter P. Chip Horrigan, Jr., of Waltham, died Monday, April 9, 2007 in his home. He was 45. Born and raised in Waltham, Chip was the son of the late Walter P. and Barbara A.( Keefe) Horrigan. He was the brother of the late Tracey M. Horrigan Chip leaves one sister, Linda S. Horrigan of Natick; two nieces, Melissa and Emily Gratz and many aunts, uncles and cousins. Relatives and friends are invited to attend Chips Funeral Mass on Friday at 9 a.m. in the Blessed Sacrament Chapel of Saint Charles Borromeo Church, 51 Hall Street Waltham. Burial will be in Mount Feake Cemetery, Waltham.