The vigil was held at Lakewood High School, where Haitham graduated in 2018. Assistant principal Susan Alvaro remembered the popular student and former track star known by many as "Mo."
"Mo, who I lovingly nicknamed 'The Perfect One,' displayed passion in everything he did, whether it was academic achievements, athletic accomplishments or personal endeavors, Mo demonstrated passion. He was every teacher's favorite. Studious. Conscientious. Helpful."
St. Petersburg Mayor Rick Kriseman was also on hand to offer his condolences.
"To Mo Haitham's family and friends, the city of St. Petersburg grieves with you in this time of profound loss," he said.
Kriseman called for national gun reform, and described the December 6th shooting as a "despicable act of terror."
"It is an act which could have been worse if not for Mo Haitham, because he is a hero who prevented the needless loss of many more lives," he said.
There were musical tributes, and then the crowd took two laps around the track, the 800 meter distance that was Haitham's favorite.
His mother, Evelyn Brady - herself a military veteran - led the way.
"I was just feeling his presence. Feeling the wind and just feeling him running alongside me saying go, 'Mama, go,'" Brady said afterward. "He pushed himself to greatness. And I am proud of that. I am proud to say that is my son. I am so proud."
At the end, Haitham's mother and his cousin, Ashley Williams, released 20 balloons to mark what would have been his 20th birthday.