The information, which includes Social Security and drivers license numbers, was on a King County sheriff's office computer that was stolen from a detective.
The laptop and a personal hard drive were full of case files, including personal information about thousands of crime victims, suspects, witnesses and even police officers.
The laptop was stolen last March from the backseat of a detective's undercover pickup truck.
To say Christie Diemond was outraged when she got a letter in the mail last Friday would be beyond an understatement.
"One of our detective's laptop computers was stolen from her vehicle," Diemond read from the letter.
The letter goes on to say that the Social Security and drivers license number of both Diemond and her deceased mother could have been compromised and they could be victims of identity theft.
"Nobody could be more shocked than I was that the King County police had lost a laptop with all my personal information," Diemond said.
The sheriff's office confirms the laptop was stolen from the truck. Officials says the detective didn't follow KCSO policy and could face discipline.
"I feel awful for them that this happened, but there was no malicious intent," said Det. Sgt. Katie Larson with the sheriff's office.
The sheriff's office is legally required to notify victims about the security breach, and last week they sent out 2,300 letters to everyone who may now be vulnerable.
Larson said it took this long to send the letters because they had to figure out who they needed to notify.
"It's not something you can just press a button and it all pops up for you," she said. "Somebody had to go through and read everything and cull out all of that information."
But Diemond said waiting three months to notify her gave potential identity thieves a head start on using her information.
"I went through the roof," she said. "I can't even believe they waited that long to tell people that. It's outrageous -- it's worse than outrageous."
The sheriff's office said this was not the first data loss they've had, but it was the largest.
They were already in the process of adding encryption software to all of their computers when the theft happened. Sixty percent of the computers were finished, but the stolen computer was not one of them.