A Florida youth flies a small plane into a skyscraper and leaves a note supporting terrorists. Another from California ends up fighting for the Taliban in Afghanistan.
Like the defendants in high-profile school shooting cases, Charles Bishop, the 15-year-old suicide pilot who crashed a small plane into a Tampa office building, and John Walker Lindh, the 20-year-old American Taliban fighter, are sometimes described as loners or outsiders.
Some experts say these latest cases are simply too complex to be compared. But others see a common thread that may also run through the school shootings. There is, they say, a sense of disconnectedness coupled with teen-age angst and impulsiveness that leads to extreme acts.
"Loner doesn't even really describe it -- they don't really know how to play the game," says John Mayer, a clinical psychologist from Chicago who has served as a consultant to the FBI and police in several high-profile cases involving troubled teens.
Vickie Beck, a child psychotherapist at the University of Maryland Medical System, agrees that it goes far beyond being a loner.
"You ask yourself, 'Is there depression in there -- that sense of isolation and powerlessness and the underlying rage against the system?'" Beck says.
At first glance, the lives of Bishop and Lindh sound idyllic in many ways.
Lindh grew up amid wealth and the fog-shrouded headlands of Marin County, just north of San Francisco.
Bishop attended a private school in Dunedin, Fla., where he played basketball and flag football, tutored first-graders and was a flag-bearer.
"I can picture him singing 'My Country 'Tis of Thee,' bellowing it out. He was proud to be an American, let me tell you," says Dale Porter, head master at Dunedin Academy, where Bishop attended the eighth grade. "Something just flipped out with him."
Exactly what that "something" was is still unknown. But Porter and others wonder if it had something to do with going from a small school of 275 students to a high school with 2,200.
At least one student at the high school described him as a "teacher's pet." But he was also characterized as one who kept to himself, spending a great deal of time in his bedroom, where authorities searched and confiscated computers after Saturday's plane crash.
Grief counselors were sent to Bishop's high school Monday. But, at least early in the day, no students had turned out talk about his suicide, said Ron Stone, a spokesman for Pinellas County School District.
Lindh was described as a gifted poet, but one who stayed in the background at an alternative high school he attended. In 1997, at age 16, he took the state high school equivalency exam and passed it -- converting to Islam that same year.
Abdullah Nana, the 23-year-old son of one of the leaders of the Mill Valley, Calif., Islamic center where Lindh first studied, called him "a sincere person, intelligent person, a quiet person." But he was one of the few of Lindh's peers who claimed to know much, if anything, about him.
Lindh would later tell his parents that he felt at home -- perhaps for the first time -- in central Asia.
Mayer says that, "while it may not be politically correct to say so," there is another factor he wonders about in these cases -- privilege.
"You don't see urban kids doing these kinds of things; they're in survival mode," Mayer says. "They don't have the luxury of going out and finding Islam in northern California or taking private flying lessons."
"Even those kids in Columbine, they had a garage full of weapons," he adds. "Where would most kids get the time, resources and parental neglect to accomplish that?"
But other experts, while hardly condoning high-profile acts of violence and rebellion, offer a more sympathetic view.
"Do we, once again with Charles Bishop, have a boy who was somehow singled out in unpleasant way at school? Was he being teased? Was he being hazed?" asks Carol Maxym, an educational consultant and author of "Teens In Turmoil," a guide for parents.
"You can tell the kids who are being picked on. And I am over and over and over again, shocked, astonished and appalled with adults who don't step in and say something."
Martha Irvine can be reached at mirvine(at)ap.org