Bill Oefelein (circled, left, on a training mission in Canada with fellow astronauts including Nowak, right, in 2004) "is a really good, strong astronaut . . . one of our best," said a NASA spokesperson. Separated from his wife, he is still "most definitely involved with his family," says close friend Agnes Cimini. "He has his kids on weekends and some holidays." Photo by: JACQUES BOISSINOT / CP / AP
Out of This World| Colleen Shipman, Lisa Nowak, William Oefelein
But Nowak's younger sister Andrea Rose told PEOPLE that Nowak and her husband had recently separated; she also said Nowak never quite recovered from losing three former classmates in the 2003 Columbia shuttle explosion. "We knew Lisa was under a lot of stress," says Rose, 41, a lawyer. "But there's no way of knowing how a particular person will react to stress. We love Lisa and we're worried about her well-being." Nowak "is a very loving mother and a caring person," adds her brother-in-law Jonathan Rose. "She was someone who played by the rules. To say this is out of character would be a gross understatement."

It's not clear what kind of relationship Nowak had with Oefelein or what role her attraction to him played in the breakup of her marriage. (She told police she and Oefelein had "more than a working relationship but less than a romantic relationship.") In any case, Nowak apparently believed Oefelein was involved with Colleen Shipman, an Air Force engineer assigned to Patrick Air Force Base near Kennedy Space Center. Shipman, her neighbors say, was unusually warm and bubbly. "If you don't have a smile," says one neighbor, "she'll give you one of hers."

Her relationship with Oefelein, it seems, pushed Nowak over the edge. According to police, Nowak drove more than 900 miles from Houston to Orlando and finally arrived at the La Quinta Inn just outside the Orlando International Airport. Wearing glasses, a dark wig and a light-colored trench coat, she went to the airport and searched for Shipman, who got off a 1:05 a.m. flight from Houston. Nowak followed her onto a shuttle van and got off at the same spot in the parking lot. Shipman heard "running footsteps coming towards her as she was getting into her car," police later recounted. "[She] feared for her safety [and] quickly entered her vehicle."