One middle school student admitted to hurling the object, the Palm Beach County Sheriff’s Office said in a news release.
The incident happened Friday around 1:45 p.m. in West Palm Beach.
The release said: ‘While assisting the United States Secret Service with a motorcade movement for President Donald Trump it was reported that a vehicle in the motorcade had been struck by what was believed to be a small hard object.
‘The incident was reported to have taken place on Southern Boulevard between Parker Avenue and Lake Avenue.’
Trump’s motorcade was coming from the airport at the time, when it took place close to his private estate Mar-a-Lago, CNN reports.
Demonstrators were at the corner as the motorcade went by, the report said.
Several members of the motorcade returned to the scene after completing the motorcade to look for witnesses and objects along the roadway.