BETHEL — Police investigating a “hang-up” call to 911 from a Governors Lane home heard a gunshot just as they arrived at the scene of what turned out to be a murder-suicide, according to a recently unsealed search warrant. Anh Cristofalo, 68, suffered a cervical spine injury and underwent surgery the day of the shooting, according to the warrant. The tenant, who moved in with his sister and brother-in-law in 1994, was initially given two months to leave the housem but the two parties agreed last fall that Pham could stay until March 25 — the day of the shooting. [...] during the search that day, police found two .22 caliber shell casings in a hallway as well .22 caliber ammunition and a .22 caliber makeshift “zip gun” in Pham’s room, the warrant shows.