Police said no one was inside the cruiser, which was parked across the street from the Retreat at Twin Lakes apartment complex, near the front of Bentley Elementary School.
CBS affiliate WKMG reports witnesses said they heard six shots. At least two bullets struck the patrol car.
Sanford police said the cruiser had been parked in front of Bentley Elementary for the past couple of weeks at the request of school officials who had concerns about safety issues.
Police removed the car from the scene, and an investigation is ongoing.
Martin, 17, was shot and killed in late February by neighborhood watch volunteer George Zimmerman, who has claimed he acted in self-defense.
Zimmerman, 28, has not been charged with a crime in Martin's death, a fact that has provoked demonstrations and calls that he be prosecuted for killing the teen.
On Monday, a group of students calling themselves the Dream Defenders marched to the Sanford police station. Six of the demonstrators wore hooded sweatshirts (which Martin was wearing the night he was shot) as they blocked the department's main entrance. Others linked arms, sang and chanted as they stood facing the building.
The demonstration closed the Police Department headquarters, and City Manager Norton Bonaparte Jr. and Acting Police Chief Darren Scott met with leaders of the student group and community leaders.
Also on Monday, the special prosecutor appointed to the case, Angela Corey, announced that she was skipping the grand jury as part of her investigation.