Long Islanders are on edge following a string of car thefts across Nassau County.

A group of thieves ransacked multiple cars on Knickerbocker Road in Manhasset Sunday morning. The thieves took various items and possibly tried to steal cars.

Security video shows a group of four masked men running up to a home. They worked quickly and efficiently, trying the doors to multiple vehicles. They were able to get into two of them because the doors were unlocked.

Dennis Yu lives down the street and says that he is concerned.

“I feel like it should not be happening in this neighborhood, so I was surprised,” he says.

But Nassau police say that they are not surprised. They say car thefts are up 207% from this time last year. They say individuals and groups of thieves are hitting every down across the county. They are looking for drivers who don’t lock their doors or those who leave wireless key fobs inside of the vehicle.

Police say that more than 350 cars have been stolen in Nassau County this year alone. Police are reminding residents to lock their cars when they park, no matter where they are.

Yu says that his security camera caught a thief trying to break into his car earlier this month. He says they were unsuccessful because he never leaves valuables in his car and always locks his doors.

“All the time. I gotta be careful. I don’t want anything to happen. I just want to keep the family and myself safer and the area safe,” Yu says.

Police say some of the thieves are looking at the side mirrors of high-end vehicles. That's because when most of those cars are locked the mirrors fold in. If they're not folded in that usually means the car is unlocked and could be an easy target.