As temperatures drop and the snow continues to come down, more people are doing something they probably know they should not do: leave cars running unattended to warm them up.
It's called "puffing," and one Denver man said that because he did it, thieves didn't just come for one car -- they came for both of them.
"The car was just parked right in front of the walkway so my wife could just step right in," said Gregory Kehrl, talking about something he has done a thousand times in his quiet Denver neighborhood. "My wife and I were getting ready to go to a Christmas party, [so I] came out, [and] started up the car."
He stepped away from his running car to check on whether his wife was ready to go ("less than 60 seconds"), and that was all it took for someone to take off in his older model Mercedes Tuesday night.
"I see this big, black pickup truck creeping up the road, no lights. and I started to run after it screaming, 'Give me back my car!'"
The thieves also got rid of his new iPhone that had a tracking function.
"They ripped off the cover, and said, 'Oh this is an iPhone,' and threw it out the window," said Kehrl. "We found it on the side of the road."
But that was not the end of Kehrl's misfortune. The thieves kept his wallet, checkbook and keys and came back later that night for his second vehicle.
"I had cable-locked the steering wheel to the door handle and moved it," said Kehrl, "But it wasn't enough."
Statistics show Denver "puffer" thefts are up, with 276 cars stolen from January through Dec. 8 this year, a 20 percent increase compared to the same time period last year.
"I feel like an idiot, but I want to warn my neighbors," said Kehrl. "When the timing is perfect, you lose. And you never know what the timing is going to be. So the advice is never, ever leave your car running unattended. And don't leave all your personal information in them."
Police have recently found both of his cars and they are now being inspected for damage. The thieves were also using his credit cards, so police are hoping to get surveillance video to identify them.
Records show only one ticket has been issued by Denver Police for leaving your car unattended -- in January 1, 2014.
Police told Denver7 remote car starters are also not legal under state law, which was enacted for environmental reasons, not to prevent auto thefts.