Officers were called to the scene around 6:40 p.m. Sunday after the child, who was riding an e-bike, was hit while attempting to cross Green Lane after exiting the school parking lot, according to Bristol Township police.
The boy was taken to St. Mary's Hospital and later airlifted to the Children's Hospital of Philadelphia. Police said he has a potential skull fracture.
Authorities said the driver remained at the scene.
Police released video showing the roadway near the high school. The footage, which has been zoomed in, shows a Toyota Camry entering the frame at the moment investigators say the boy was struck.
A witness, Aiden Coley, described what he saw: "It almost sounded like the tire popped. I see the bike fly onto the sidewalk, and I just hear all this screaming."
Another person, Tony Mateo of Bristol Township, recalled the scene when he arrived.
"He looked young. Just the way his family was surrounding him," said Mateo.
Police said they are still investigating the circumstances surrounding the crash, including how the young child came to be riding the e-bike.
"The age is staggering. This is a rather large bike that has some significant power," said Sgt. Jason Mancuso of the Bristol Township Police Department.
A family member, who didn't want to be named, spoke to Action News to dispute the police report.
The family member says the bike belonged to the child's teenage brother, and while the 5-year-old was sitting on the bike at the time, it was powered off.
The family member said the victim and his brother were waiting to walk across the street with the bike to come home when they were hit by a speeding driver.
Residents in the area said they frequently see children riding e-bikes near roadways.
Bob DiDonato of Morrisville said, "Some of them run out in the road and they don't look, and a lot of them are on bicycles too. And not only that, but our drivers around here like to go a little fast."
Authorities noted that most e-bikes in Pennsylvania have a minimum age requirement of 16.
Mancuso also urged caution among parents.
"If you're a parent and your child wants one, think twice. These are very dangerous. They go very, very fast," said Mancuso.
Police are asking any witnesses who have not yet come forward to contact investigators.