KOURTNEY KARDASHIAN’s 2-year-old son Mason was fool­ishly put in grave danger when baby dada SCOTT DISICK left him alone in a parked car in sweltering heat, says eyewitness.

The horrifying incident allegedly took place Aug. 10 in Calabasas, Calif. – where temperatures that day soared as high as 107 degrees!

Scott, 29, had a lunchtime meal with his little boy at a restaurant and then drove to a nearby street-corner newsstand. There, according to the eye­witness, he parked his Mercedes SUV, turned off the ignition and left Mason alone in the vehicle while he went off to browse through magazines.

“He was out of the car for at least five minutes and should have never left his son alone!” an eyewitness told The ENQUIRER. “The car was parked in the hot sun with the boy alone in the back. The car was not running, so the air-conditioner wasn’t on and the windows were rolled up.”

A newsstand employee who knew Scott as a regular customer, confirmed to ENQUIRER the details of the eyewit­ness, adding: “Scott ended up buying a boating magazine.”

We showed exclusive photos of the incident to safety expert Amber Rollins of KidsAndCars.org, and she’s convinced Scott put his son in mortal danger.

“I was shocked when I saw the pho­tos. Leaving a child in the car, even less than five minutes, can be deadly. Cali­fornia is one of 19 states that has a law against leaving a youngster in the car.”

In fact, a woman in a town near Cala­basas was recently arrested by police, and faces two years in jail for leaving her two young children in a locked car to go shopping for 25 minutes.

Medical expert Dr. Gabe Mirkin, a board-certified pediatrician in Orlando, Fla., told The ENQUIRER that the effect on the brain of being inside such a hot car for even a short time would be like an egg white hitting a heated griddle.

“It was highly irresponsible and dan­gerous to leave a small child in a car even for a short period. With the sun beating down, it could get as hot as 130 degrees inside,” said the physician. “This can re­sult in a fatal heat stroke.”

The Los Angeles County Sherrifs’ Dept. is not investigating because it was not contacted at the time of the incident. However, the Sheriff ’s Dept. pointed out it is illegal to leave children under 6 alone in a vehicle.

When a badly shaken Kourtney heard about the frightening incident, she flew into a rage, a family in­sider told The ENQUIRER. The 33-year-old mom, who had the couple’s second child Penelope in July, was a wreck, divulged the source.

“All she could think about is that Mason could have died. She read Scott the riot act, and so did her sisters Kim and Khloe. They don’t want Scott taking the kids anywhere now unless someone is with him. Kourtney was shaking and in tears, and she called Scott everything in the book. They can’t be­lieve Scott could be so mindless and do something potentially so disastrous.”