WASHINGTON (AP) — The FBI says the 2017 fatal shooting by U.S. Park Police of an unarmed Virginia motorist is a complex case and that its 16-month investigation is not unusual.

The bureau’s comments came in a March 15 letter to U.S. Sen. Charles Grassley, R-Iowa, who has questioned why the FBI is taking so long to investigate the shooting death of 25-year-old Bijan Ghaisar of McLean. The FBI said it can’t provide a detailed response while the investigation is ongoing.

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Ghaisar died after a November 2017 chase on the George Washington Parkway. Ghaisar’s family filed a federal lawsuit seeking $25 million and answers about what happened.

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A video released by Fairfax County Police shows officers shooting Ghaisar after he stopped his car, then started to drive off.

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