(CN) – The FBI paid $900,000 to access the iPhone of one of the shooters in the 2015 San Bernardino shooting that left 14 people dead, a Democratic senator has revealed.

The agency announced it had unlocked the iPhone of San Bernardino gunman Syed Farook in March 2016, after a protracted battle with Apple over consumer privacy. The matter eventually wound up in court.

In a statement at the time, U.S. Attorney Eileen Decker said the FBI sought an order compelling Apple to unlock the phone to “fulfill a solemn commitment” to the victims of the shooting. Apple maintained the request was wrong, and that creating a backdoor into the phone would have “set a dangerous precedent.”

Sen. Dianne Feinstein revealed the cost of breaking into the phone during questioning FBI Director James Comey at a Senate Judiciary Committee oversight hearing Wednesday.

The FBI for the last year has treated that figure as classified information and has not disclosed it. The bureau has also protected the identity of the vendor.

The Associated Press and other news organizations last year filed a public records lawsuit for that information.