Flowers mark the sidewalk where Richard Henderson helped countless children cross the street.

There were tributes to a crossing guard who was killed this weekend on the subway.

“He was a person that always cared for the wellbeing of the students no matter their age and always made sure people felt safe,” Leo Prince said.

Prince is a 10th grader at Avenues The World School, a private pre-K through 12th grade in Chelsea, where Henderson worked as a crossing guard for a decade.

Police said Henderson was shot to death on Sunday just before 9 p.m. on a Manhattan-bound 3 train as it approached the Franklin Avenue station in Brooklyn.

According to police, he was breaking up a fight that he was not involved with when one of the people fighting took out a gun and opened fire.

Students describe him as a “guardian to all those lucky enough to know him.”

“I remember he used to play football with us at the park when we were younger in the field because he would help walk us,” Prince said.

Judy Fox, head of Avenues The World School, released a statement: “He was an amazing man who radiated kindness and joy. His loss will be deeply felt across our entire campus community and we are committed to honoring his memory and the incredible legacy he leaves behind.”

Prince set up a GoFundMe that has raised more than $200,000. The page was created to help Henderson’s family cover his funeral expenses, support his children and grandchildren to provide them with the means to get through this difficult time.

“It is the contribution of every student, every person who knew Rich,” Prince said. “Our hearts are broken,” Richard Davey, president of NYC Transit, said on NY1’s “The Rush Hour” Tuesday.

Davey said there were no cameras on the Manhattan-bound 3 train, but he’s hoping station cameras help the NYPD in the investigation.

“He was a hero,” Prince said.

Students said they want to see the killer of someone they respected so much held accountable.