Police say Joshua Powell initially refused a follow-up interview Monday, then met with investigators on Tuesday but only answered some of their questions.
"It breaks our hearts but we're not surprised (after) watching his actions and reactions over the past week," family spokeswoman Shelby Gifford told reporters at a press conference Thursday where the missing stockbroker's family and friends cried, held up photos of the dimply, 28-year-old mother of two, and said they still hope she is found alive.
"If you see Susan, note the location and call 911 immediately," said Gifford, who removed her glasses, wept, and added: "Susan is a mother, a daughter, an aunt, a sister, a niece, a granddaughter, and a friend. She's loved by many. Our primary focus is to remind everybody that Susan has not been found."
Joshua Powell has told investigators he last saw Susan at their house in West Valley City, southwest of Salt Lake City, on the night of Sunday, Dec. 6, when he took their 2- and 4-year-old sons for an overnight camping trip. When they returned the following afternoon, Powell says, his wife was gone.
Friends and family members say the story is odd and that Susan would not have taken off without her children.
"Susan is an excellent mother and would not have tolerated her children being taken out after midnight to go camping in such dangerous and cold conditions," Gifford says.
Still, family members say they remain hopeful Susan will be found alive. They will hold a candlelight vigil Friday night in Susan's home town of Puyallup, Wash., and next week, Susan's father, Charles Cox, will return to the Salt Lake City area to continue working with police and aiding in the search for his daughter.
"I feel just totally helpless, and what I hope to accomplish by going back down there is to keep the focus, keep her face out in front of people … so we can bring her home," Cox says.
Susan's brother, Kirk Graves, tells ABC News he "wouldn't be surprised if (Joshua) gets arrested in the next seven days," but police say they have no timeline or plan for making such an arrest.
Powell's criminal attorney, Scott C. Williams, did not return a call seeking comment.
Family members have set up a Facebook page to share information and potential sightings.