The House of Representatives is expected Thursday to honor Gabe Zimmerman, the congressional aide who was killed in the January shootings in Tucson that injured Rep. Gabrielle Giffords, by dedicating a room to him. Zimmerman, who was 30, served as Giffords’s community outreach director. The shooting, which took place at a constituent event that Zimmerman had organized, left him and five others dead, including federal judge John Roll and 9-year-old Christina Taylor Green.