Dwyane Wade addresses the Stoneman Douglas High School graduates with the theme of starting a new chapter in their lives. (1:32)

Dwyane Wade, reflecting on the challenges faced by the students at Marjory Stoneman Douglas High School, where a mass shooting took place last year, told the school's 2019 graduating class that "I've never experienced anything to the magnitude that you guys just experienced."

Wade was a surprise speaker for the high school's graduation ceremonies Sunday. In his speech, he shared his perspective on his first visit to the Parkland, Florida, school in March 2018, three weeks after the shooting that killed 14 students and three staff members.

"I remember walking to the school, and I remember hearing absolutely nothing," Wade said. "I remember thinking to myself, 'I've never heard this kind of silence before in my life.'"

Wade then related his surprise at the reaction he got from people at the school, saying they made him a part of the "MSD family."

"As I was walking in, students started seeing me, I remember seeing smiles, people running, pulling out their phones," Wade said. "... I remember thinking, 'Wow.' It was packed. I didn't expect that."

Wade told graduates that it was understandable if they felt unsure about their futures. He said that in some ways, after 16 years in the NBA, he also was unsure exactly what his future entails.

The now-retired Wade has been a regular supporter of the school ever since the shooting. He said he was honored that Joaquin Oliver, who was killed in the attack, was a huge fan of the former Miami Heat star and was buried wearing a Wade jersey.

Wade closed his remarks by asking those in attendance to join him in a cheer that he used to spur on the Heat in the 2013 NBA Finals.

The cheer was punctuated by the words "to the last man, to the last minute, to the last second, we fight, we fight, we fight!" Once he led the graduates and their guests in the cheer, he wrapped up his speech by again saying, "MSD Strong" -- the school's mantra since the tragedy.

The Associated Press contributed to this report.