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.
Lopez, a Santa Rosa eighth-grader, was born in Sonoma County but his parents are from Sonora, Mexico.
He was shot seven times Tuesday on a sidewalk in southwest Santa Rosa by a veteran sheriff's deputy who reportedly mistook the plastic BB gun the boy was holding for an assault rifle.
Santa Rosa police are investigating the shooting under a long-standing local protocol that hands over such "critical incident" inquiries to a separate law enforcement agency.
Schwedhelm voiced confidence in his department's ability to complete a full and thorough inquiry.
"We're a professional policing organization," he said.
At the same time, citing "witnesses" interviewed in various media reports this week, Schwedhelm issued a plea to anyone who saw the shooting to come forward, saying his investigators want to talk to those people.
"We're following up on every investigative lead we have," he said.
Authorities declined Friday to provide answers to a number of questions about the final moments leading up to the shooting, at 3:14 p.m. in an unincorporated neighborhood of southwest Santa Rosa.
Investigators have yet to say whether or not the two deputies who drove up behind Lopez near Moorland and West Robles avenues identified themselves as law enforcement before ordering him to drop the gun.
The boy initially had his back to the deputies when the orders were issued, police have indicated.
They also have yet to confirm whether the deputies had turned on their cruiser's siren before issuing the orders. A witness told police he thought he heard the chirp of the vehicle's siren, but the deputy at the controls "indicated that he wasn't sure if he'd turned the siren on or not," Santa Rosa Lt. Paul Henry said Friday.
Henry said he did not believe Lopez had any earphones or buds on at the time, but added Friday that he had not asked that specific question of investigators.