Many of the victims of the Brussels attacks have not yet been confirmed dead, even those whom news organizations have listed under "deceased."

This is what Laurent Duhaut discovered when he saw a photo of his best friend flash across the television screen following the attacks on Tuesday morning.

Oliver Delespesse was the first person Duhaut met on his first day of college in the late 1990s. After becoming fast friends, the two remained close for some 20 years. For Duhaut, Delespesse was part of what made Brussels home.

Duhaut posted a photo of his missing friend online, and saw it reappear in the media as one of the attack victims

The chaos on Tuesday left many without information for hours. As the day progressed, Duhaut and Delespesse's family became increasingly worried when they couldn't contact him.

His employer, the Wallonia-Brussels Federation, has said he was killed during his regular morning commute.

However, according to Duhaut, investigators have only been able to confirm that his subway ticket had been scanned shortly before a bomb ripped through Maelbeek station.

'A question of survival'

A soft rain slowly trickles down the windows of the café where Duhaut and Delespesse often met over a meal or a drink. It's Good Friday, a somber day in Christian countries and, today, in Brussels especially, a gray day that matches the mood of a city trying to cope with tragedy.

After nearly an hour discussing his friend, pictures of the 45-year-old he describes as a bon vivant with a great sense of humor bring tears to Duhaut's eyes for the first time.

"For us, he's still alive until there is an official death certificate. We will keep fighting to believe in that and continue to send him positive energy," he says, adding that it was "a question of survival."

Between the suicide bombings at Brussels Airport and Maelbeek station, some 300 people sustained injuries. Many also emerged from the destruction completely disoriented, Duhaut says. Another possibility is that his best friend is lying in a coma or is too disfigured to be identified.

Doctors face unprecedented challenges

Thirty kilometers (17 miles) to the east of the Belgian capital, surgeons at the University Hospital in Leuven - one of the main arrival points for the airport victims - operated on 15 patients within two hours after the explosions.

Medical staff saw "horrible things" that they'd never seen before, according to Paul De Leyn, who heads both thoracic and general surgery, and his colleague Stefaan Nijs, who is in charge of trauma surgery.

Screws and metal from the bombs tore through the extremities of many victims. Many suffered from severe burn wounds and eye damage from the bombs.

Doctors Nijs and De Leyn are proud of the cooperation among staff at their hospital after the attacks

Whoever carried out the attack clearly intended to "create as much harm as you can to a human being," Nijs said.

Neither could comment on the identification process, but they did note that the hospital had contacted next of kin for all of the patients who underwent operations by midnight on Tuesday.

Living in the moment

In Brussels, small piles of flowers, notes and tea lights have grown outside of the Maelbeek station entrances each day since the attack.

By Friday, rain had washed away many of the multicolored chalk messages of love and peace.

"If people tell me in the next few hours that he's dead, I will have to live with that," DuHaut says.

To Duhaut the feeling of sadness presents a paradox: he's received many messages of condolence, but he still hopes for his friend's return.

"I have so many good memories with him and we have gone through so many things together. No one can take that away from me," he says. "It's important to live in the moment."

Lisa Louis contributed reporting from Brussels.