A man unloading his father’s groceries in St. Paul looked out the window Monday to see someone stealing his car — and he ran after the thief.

The 36-year-old held on to the driver’s side door of his Toyota Corolla, and ran and slid down the street with the car for about three-quarters of a block as the male drove away, said Steve Linders, a St. Paul police spokesman.

St. Paul police received at least nine reports on Monday of people having their vehicles stolen after leaving them unattended with the keys in the ignition. The department is sounding the perennial alarm Tuesday about how easily cars can be stolen if people leave them warming up.

In the case in Summit-University on Monday afternoon, as the Corolla’s owner held on to his car, he made eye contact with the auto thief and told him not to steal it, but the suspect drove on, Linders said. It happened in the 900 block of Fuller Avenue shortly before 4 p.m.

A 31-year-old witness jumped onto the Corolla’s trunk to try to stop the thief, who appeared to be a teenager.

“He told the officer he just reacted and he wondered, while he was on the car, how he was going to get off the trunk,” Linders said, adding he fell off after about a block. No injuries were reported.

At about 6:30 p.m. Monday, someone called police to report finding a car parked in his driveway in the 600 block of Fuller Avenue and it turned out to be the Corolla. A cellphone and keys were missing from the car, Linders said. Police had not made an arrest as of Tuesday afternoon.

The other auto thefts were reported Monday in neighborhoods throughout St. Paul — in Conway, Frogtown, Greater East Side, Merriam Park, Payne-Phalen, St. Anthony Park and Summit Hill.

“People don’t realize that just warming your car up for convenience can end in some serious consequences,” said Sgt. Mike Ernster, a St. Paul police spokesman. “It can cause all sorts of problems … and it’s all preventable.”

It’s also against St. Paul ordinance to leave a car unattended and running, unless it’s a remote-start system.