When it happens to you, you have to bear witness.

At some point, everyone faces it -- one of those awful or unthinkable tragedies that we know is inevitable but that we strive mightily not to imagine. At any given moment somebody, somewhere, is contending with it.

The rest of us are choosing whether we will bear witness.

This week, it couldn't have been clearer to Roger Harris of the Shepherd Park neighborhood. His only child, Keisha, is a freshman at Xavier University in New Orleans. On Sunday, she called him on her new cell phone from inside the dark, sweltering dorm where administrators had gathered its remaining students to await plans that never materialized. On Tuesday, the phone became useless after a college administrator who'd borrowed it returned it with the battery drained.

The next day, Harris e-mailed me about Keisha's situation, bringing it -- Hurricane Katrina -- home for me. Not that I welcomed it. Last week, while preparing my sons for school, I got news that put me on a Chicago-bound plane, then dashing to my childhood church in Indiana.

To bear witness.

My late father's sister had died. Nothing seemed as important as cradling my sobbing mother in that hushed sanctuary as mourners described their sorrow over losing my beloved Aunt Marian.

For several days, Katrina barely registered. But as the surrealness of my personal loss receded, awareness of this much larger it grew -- even as I avoided the endless hurricane-related news accounts.

The spirited aunt who'd adored my father and sewn up my always-ripped pants was gone. The death toll in Iraq kept surging. Nearly a thousand had died in a fear-fueled Baghdad stampede.

All I wanted to do was turn away.

But when a friend told me about a stricken-looking man on the news whose life-mate had been swept away, I turned on the TV and faced it. By the time I got Harris's e-mail describing Keisha as being "among approximately 400 people that were unable to leave campus . . . now trapped in dormitories with dwindling food and water," I felt ashamed of my desire not to bear witness.

Professionally, Harris -- who was divorced from Keisha's mother, Faye Vaughn-Cooke, when their daughter was 6 -- has faced it time and again. A supervisor for the Federal Emergency Management Agency, he last year helped the government manage four hurricanes.

But this time, it concerned a wannabe pediatrician who enjoys "CSI" and James Patterson thrillers, and who chose Xavier for its renowned pre-med program. "She's my heart," Harris, 53, explained. "This is different from what I deal with every day. It tears at my heart that I can't go there, can't bring my daughter home."

Harris did what any parent, any government employee with connections, would do -- went through FEMA channels until he reached someone with authority in the hurricane-affected region. That employee, he said, told him "he had to pass me on to state emergency services. And then he said, 'I wish you luck.' "

"I wasn't asking anyone to rescue my daughter, just to check on her," Harris explained. "I've had no contact with an adult to tell me what's happening."

Harris's "heart" arrived at Xavier for summer orientation in June, but was sent home early by administrators when Tropical Storm Cindy loomed. So Harris felt "fairly safe" as Katrina brewed. Clearly, Xavier was experienced with evacuating hurricane-endangered students.

Last Friday, Keisha informed him that administrators were closing the school. By Saturday, staff members had gathered students into their dorms, which Harris assumed would be the location from which they would be evacuated.

But rumors swirled: There was no money for buses; no transportation could be found. By Sunday, students had been moved to the dorms' upper floors, their beds pushed into hallways. Through the night, Keisha updated her father on the howling winds, and on the students who were hyperventilating or becoming hysterical.

Night turned to day. The lights and air conditioning failed. Toilets backed up. By Monday, even the self-possessed Keisha sounded anxious. Why, her father asked, weren't school administrators informing students, contacting parents? Then Keisha's cell phone died.

At 7:30 p.m. Wednesday, Harris's phone rang. Keisha, on a borrowed cell phone, relayed that she was hot, nervous and still clueless but okay. Hearing her voice "was like two tons of bricks being taken off your shoulders," Harris told me.

Then silence. More futile checking for information with government, media and Internet sources. More learning, Harris said, about the "lawlessness happening down there that a 17-year-old girl has no business being around."

Around noon yesterday, the father of Keisha's roommate phoned; students had been ferried from the dorm to an overpass. A co-worker told Harris that the youths were on Houston-bound buses. Harris felt "a great load had been lifted" -- until he read on a Web site affiliated with the Times-Picayune newspaper that students remained on the overpass.

As of late last night, neither Harris nor his ex-wife knew Keisha's whereabouts. "She's out of that dorm," Harris said with some gratitude.

"But everything else is uncertain," he continued. "You're seeing these armed gangs -- if I know my daughter, she has her laptop in her book bag. . . . I am a very calm person. People come to me to share their problems. That's my strength."

But not now. Not with it still so much with him. Not even when those who'd rather look away must bear such terrible witness.

"Now, I am upset," Harris said. "And I am scared."