Story highlights Police got first reports early Monday that 4 Smart cars had been tossed

It all happened within a residential area of San Francisco

Authorities don't have a motive, nor has anyone been arrested

Smart cars are good for the environment, good for parking in cramped cities and good for a driver's bottom line.

Then again, all that thinking gets turned upside down when the vehicles do.

That's what happened to four of these fuel-efficient vehicles in San Francisco, tossed aside like a piece of trash.

Why? Authorities don't know, leaving Bay Area residents to speculate that anything from pranksters to people upset about hipsters.

All Brandon Michael knows is what he saw -- a group of men, in the dark of night, walking up to one Smart car.

"(They) all just huddled around it and then just lifted it up and set it on its hind legs," Michael told CNN affiliate KRON.

The basically vertical vehicle that Michael described -- its front lights pointing toward the heavens -- wasn't alone. Two others in the same 1- to 2-square mile area were flipped on their side and one was on its roof, according to San Francisco police spokesman Gordon Shyy.

Tossing a Smart car isn't necessarily easy, unless you compare to other vehicles. Unoccupied, a typical one weighs just over 1,800 pounds; a Ford Explorer, by contrast, clocks in at about 4,500 pounds.

Authorities have launched a felony vandalism investigation since the first calls came in around 1 a.m. Monday, said Shyy.

The police spokesman said witnesses identified the culprits as six to eight individuals dressed in black. If they end up convicted, they could be facing jail time and a felony.

Authorities haven't identified any suspects yet, and the fact the flippings took place in residential areas -- where surveillance video isn't likely -- makes the investigation a challenge.

Florence Dabokemp, a San Francisco resident and Smart car driver, speculates people simply acting out are to blame. And while she hasn't been victimized, Dabokemp says she's not sure what she'd do if that did happen.