A Port St. Lucie man says he learned a valuable lesson in gun safety after his stolen gun was secretly returned—with a disturbing message.

Mike Maisonneuve told local police that a gun with bullets and a knife were stolen from his unlocked car in his driveway, WPBF-TV reports.

But when he started to go back into his house, he noticed a bag next to the door with words scrawled on both sides.

One side read: LOADED GUN unlocked car = STUPID!!

The other side read: LOTS of children in area.

Inside the bag were his gun and the knife. But no bullets.

"I learned a lesson, a valid lesson" Maisonneuve told the television station. "I should not carry a loaded firearm in my car.

"My mind's been other places the last week or so. I thought I locked my car. Apparently I didn't," he said.

Interestingly, police are still looking for the person who swiped and returned the gun and knife. He or she could face charges of armed burglary, WPBF reported.