ATLANTA -- Investigators are looking for the cause of a deadly bridge collapse at the Atlanta Botanical Gardens that killed one person and injured 18 others.

Mike Alsip, a forensic investigator with the Fulton County Medical Examiner's Office, identified the man killed as 66-year-old Angel Chupin of Marietta.

Saul Chupin, overwhelmed by sorrow, fights to speak through his tears and wonders why his father had to die.

"My father, he's dead," said Saul Chupin.

Angel Chupin, a 66-year-old construction worker, fell from the Canopy Walk as it collapsed at the Atlanta Botanical Garden less than a week before Christmas.

Eighteen other workers were injured.

Chupin migrated from Mexico in the early 1990s.

He had planned to head back to his home country for holidays to see his young daughter.

Judith Rivera is the cousin of Adelfino Zuniga, one of the injured workers.

She says her cousin heavily sedated and in critical but stable condition at Grady and in lots of pain.

Eleven others are still here as well, seven in critical condition.

Rivera like Saul Chupin wants to know how this terrible incident could have happened.

"I wish OSHA would get their investigation settled so I know why," said Rivera.

CBS 46 asked OSHA and Hardin Construction, the contractor working on the walkway, why it collapsed and if it could have been avoided.

Both the agency and the company said they are waiting for OSHA investigators findings before they respond.

OSHA has up to six months to complete the investigation.

For Rivera, that's a long time to wait for answers.

"They need to make it right for these people," said Rivera.

The incident happened around 9 a.m. at the entrance to the gardens on Piedmont Avenue at The Prado. Police said there were at least 30 people on the bridge when it gave way.

Workers were pouring concrete for a new 600-foot, 45-foot long canopy walk when the bridge collapsed. It appears the victims are all construction workers, according to investigators.

Electrical worker Juan Padilla and his partner were taking a break from doing work under the bridge at the time of the collapse.

"It sounded like an explosion," said Padilla.

Investigators said when they arrived, several people were on the ground not moving.

A Grady Hospital spokesperson said 16 of the 18 victims were taken to Grady Hospital. The two other victims were taken to Atlanta Medical Center.

"The orthopedic injuries are potentially debilitating," Salomone said.

Padilla said he knew many of the victims, and fought back tears.

"It was so tough," he said. "I feel very lucky. Me and my partner, we could have been under the bridge."

The Occupational Safety and Health Administration has an officer at the scene. The agency will determine whether any safety rules were broken.

"Our hearts go out to the family of the person that was killed," said Bill Pinto, president of Hardin Construction Co.

The bridge is part of a walking trail and arched over a ravine. The garden is located next to Piedmont Park, which is popular with joggers and dog owners.

"Living this close to this intersection near Piedmont, we hear a lot of crashes and things occasionally, but I've never heard anything of that nature," said witness Emma Kate Young. "When I saw the construction worker running, that's when I thought it must be something really bad."

A statement made by the Atlanta Botanical Garden posted on their Web site said, "At this time, our primary concern is to ensure that injured individuals are properly cared for and that their families are properly contacted and receive the assistance they need. Our hearts go out to the families of all of the injured as well as the family of the individual who was killed."

The Gardens will be closed throughout the weekend out of respect for the injured workers.

Stay with CBS46.com throughout the day for updates on this developing story.