Most videos of the incident shared by witnesses had been scrubbed off Chinese social media by Tuesday morning, but some footage still online showed dozens of people lying on the ground and being attended to by paramedics and bystanders.
Chinese President Xi Jinping has called for “all-out efforts” to treat the injured and “severe punishment” for the perpetrator.
The incident has taken place amid heightened security in Zhuhai, which is hosting a major international military airshow this week.
Initial investigations suggested the attack had been triggered by Mr Fan’s unhappiness over a divorce property settlement. Because he is still in a coma, he has yet to be questioned, police say.
It is common in China for stadiums to be used as regular exercise grounds by locals.
One eyewitness, Mr Chen, told Chinese news magazine Caixin that at least six groups had been at the stadium for their regular walks when the incident happened.
The groups use a designated walking path that traces the stadium’s perimeter.
Mr Chen said his group had just completed its third lap around the stadium when a car suddenly charged towards them at a high speed, “knocking down many people”.
“It drove in a loop, and people were hurt in all areas of the running track – east, south, west, and north,” another eyewitness told Caixin.
The incident occurred 40km (24 miles) away from another venue where the high-profile Airshow China began on Tuesday.
China is showcasing its newest warplanes and attack drones at the show, which top Russian defence official and former defence minister Sergei Shoigu is expected to attend.
Several entrances and exits to the sports centre were closed during the airshow to facilitate “control”, the centre’s management said on Tuesday.
China has seen a spate of violent attacks on members of the public in recent months.
In October, a knife attack at a top school in Beijing injured five people, while in September, a man went on a stabbing spree at a supermarket in Shanghai, killing three people and injuring several others.
Also in September, a 10-year-old Japanese student died a day after he was stabbed near his school in southern China.
Following Monday’s car attack, Japan’s embassy warned its nationals living in the country to avoid speaking Japanese loudly in public.