A man fired from a Texas auto dealership used an internet service to remotely disable ignitions and set off car horns of more than 100 vehicles sold at his old workplace, police said yesterday.

Austin police arrested Omar Ramos-Lopez, 20, yesterday, charging him with felony breach of computer security.

Ramos-Lopez used a former colleague's password to deactivate starters and set off car horns, police said. Several car owners said they had to call tow trucks and were left stranded at work or home.

"He caused these customers, now victims, to miss work," Austin police spokeswoman Veneza Aguinaga said. "They didn't get paid. They had to get tow trucks. They didn't know what was going on with their vehicles."

Ramos-Lopez was in the Travis County Jail yesterday with bond set at $3,000. The Associated Press could not find a working phone number for his family.

The Texas Auto Center dealership in Austin installs GPS devices that can prevent cars from starting. The system is used to repossess cars when buyers are overdue on payments, said Jeremy Norton, a controller at the dealership where Ramos-Lopez worked. Car horns can be activated when repo agents go to collect vehicles and believe the owners are hiding them.

"We are taking extra measures to make sure this never happens again," Norton said.

Starting in mid-February, dealership employees noticed unusual changes to their business records. Someone was going into the system and changing customers' names, such as having dead rapper Tupac Shakur buying a 2009 vehicle, Norton said.

Soon, customers began calling saying their cars wouldn't start, or that their horns were going off incessantly, forcing them to disengage the battery. Norton said the dealership originally thought the cars had mechanical problems.

Then employees noticed someone had ordered $130,000 in parts and equipment from the company that makes the GPS devices.

Police said they were able to trace the sabotage to Ramos-Lopez's computer, leading to his arrest.

Norton said Ramos-Lopez didn't seem unusually upset about being fired.