ORLANDO, June 14 -- Thousands of people rallied in Southern U.S. city Orlando's downtown Monday night for the first official vigil to commemorate the victims in Sunday's deadly mass shooting.

People from all around the state of Florida gathered at the lawn in front of the Dr. Phillips Center for the Performing Arts, holding praying signs and candles. Some of them laid flowers and wrote encouraging words on the pavement with crayon.

"Tonight we remain a city of pain, we are mourning and we are angry," said Orlando Mayor Buddy Dyer in a speech during the vigil.

Fifty people, including the gunman, were killed and 53 others wounded early Sunday in the shooting at an Orlando gay nightclub. It was the worst mass shooting in U.S. history and the deadliest terror attack since the 9/11 terror attacks in 2001.

Hospital officials told local media that five people are still in "grave condition" after they were wounded in the attack.

Orlando Regional Medical Center said 29 people are still at the hospital and a number of patients remain critically ill and in shock. Six more surgeries on the victims are scheduled for Monday.

Dyer applauded the effort made by police officers, first responders and people who lined up to donate blood in the aftermath of the incident.

"We will get through this because in our city's darkest hour, our residents have shown that they are the light," Dyer added.

Many people volunteered to bring flowers, signs, food and water for the people attending the vigil.

"It's so important to do something instead sitting at home paralyzed," said Eileen Simoneau, a volunteer who hands out waters at the event.

Dyer also noted that city officials had identified all 49 victims and notified their relatives.