It was supposed to be a quiet, romantic dinner for Lea Guilbeault and Hani Beitinjaneh, who were enjoying a summer evening at the Mikasa Sushi Bar on Peel St. in the heart of downtown Montreal.

Instead, Beitinjaneh was left shocked and horrified Thursday evening as a concrete slab fell from high above, crashing through the atrium window of the restaurant and falling on his 33-year-old wife, killing her instantly.

Police and paramedics rushed to the scene to treat Beitinjaneh, also 33, who suffered serious injuries to his right hand and was in a state of severe shock.

"I saw him getting in the ambulance and he was totally devastated. He was yelling at everybody and crying," witness Justine Lafond told CTV News.

Montreal Const. Olivier Lapointe said the Beitinjaneh's hand was crushed by the falling concrete.

"He may have lost a few fingers but he's in hospital in a stable state," said Lapointe.

Lapointe said it was not yet clear what caused the decorative slab -- which weighed between 700 and 800 lbs -- to fall.

"For us at this moment, it looks accidental. There was no one who played with the block of concrete trying to make it fall," Lapointe said.

The slab of concrete fell from the 18th floor of the Marriott Residence Inn, smashing through the ceiling of the enclosed glass section of the restaurant, located at street level.

"It hit the woman right on the head, and her head was smashed..." said Kali Subramanian, a witness who became emotional while describing what he saw.

"It's's a sad way to die. Somebody eating at a restaurant, and it happens like that."

Statement from hotel

The Marriott Residence Inn issued a statement Friday morning, expressing their condolences to family.

"Marriott takes the safety of its guests very seriously. Our thoughts and prayers are with those involved and their families."

The statement noted that "the hotel is cooperating fully with the investigation."

How did it happen?

Hellen Christodoulou, an engineer, told CTV News the concrete may have fallen because of corrosion or water seepage.

But Christodoulou said it was hard to explain why only one panel fell.

"Why that particular panel, as compared to other panels? Because obviously the attachments are quite similar throughout the building," she said.

Investigations underway

The circumstances surrounding Guilbeault's death are being investigated by Quebec Coroner Jacques Ramsay.

Quebec's construction board, the Regie du b�timent, is also conducting an investigation and evaluating the structural integrity of the hotel.

Board inspectors carried out a routine inspection in 2000, but follow-ups and maintenance are up to the Marriott Hotel.

"We never received any complaints about this building," said Christine Grant of the board.

Built in 1967, the tower has dozens of decorative pre-cast slabs.

In his 30 years inspecting and repairing buildings like these Normand Tetreault says he's surprised to see this kind of damage.

"I've seen many pieces coming off, corners of panels, but it's only the second time that I see a complete panel coming off," said Tetrault.

The construction board has requested the Marriott ensure the building's facade is safe.

In a statement, the Regie said it is up to building owners to ensure that their premises are safe and are checked regularly.

If the public has any concerns, the Regie can be reached at 1-888-271-1827.

With files from The Canadian Press