The federal intervention is rare. The last time the FBI investigated a local officer-involved shooting was in the 1997 death of Kuan Chung Kao, a Taiwanese national killed by a Rohnert Park officer. The shooting enraged Chinese cultural groups, but the FBI investigation and separate state and local inquiries found insufficient evidence to file criminal charges.
Lopez's death has stirred perhaps even stronger community emotions.
He is the youngest person to die in an officer-involved shooting in Sonoma County, according to Press Democrat records stretching back to 1969.
Schwedhelm said the FBI, to his knowledge, had not played any role in the investigation led by his department into the Tuesday afternoon shooting.
A lieutenant in the police department fielded a call from the FBI notifying them of the agency's decision.
For Freitas, it was a sheriff's captain who got the word.
"They notified us what they were going to do and we said 'Great we'll welcome that,'" Freitas said.
The sheriff said his office would also press ahead with its own internal investigation of the shooting.
Any finding by the FBI ultimately could wind up in the hands of the U.S. Attorneys' Office.
The development could focus even greater attention on a rapidly evolving local story that has spurred a groundswell of community reaction, fueling daily marches and vigils, and drawn national and international attention, including the interest of the Mexican government.