Agents with the San Francisco field office of the Bureau of Alcohol, Tobacco and Firearms (ATF) announced late Thursday that they had made two arrests in connection with the Halloween shooting in Orinda, and said they seized a weapon linked to the crime.

The announcement by federal authorities came days after the Contra Costa County DA's office declined to file charges against any of the five men arrested late last week. As NBC Bay Area first reported, the ATF said that a gun it recovered Thursday has been linked through its ballistics database to multiple shootings in the Bay Area, including the one on October 31 in Orinda. The agency also announced that's now offering a $20,000 reward for new information that could lead to a conviction in the shooting.

Anyone with information is asked to call 888-ATF-TIPS (888-283-8477) or visit

It is not clear if the two people taken into custody by the ATF are new suspects or re-arrested individuals who were freed earlier this week. As the Chronicle reports, it's also not entirely clear if the gun the ATF identified was seized during these new arrests, or during the five arrests last week, in which the ATF participated.

The investigation is ongoing into what Contra Costa County Sheriff David Livingston has described as a very complicated crime scene, and "a bloodbath." Two of the five victims in the shooting, Javlin County and Raymond Hill Jr., had guns on them when they died and may have themselves been responsible for one or more of the deaths. As we learned last week, Hill was associated with the SF-based gang called the Page Street Mob and he had recently been paroled after being convicted for a drive-by shooting in Potrero Hill. County has reportedly been linked with a gang in Marin City, as have two of the men arrested last week and since released, 20-year-old Jaquez Deshawn Sweeney, and 20-year-old Jason Iles.

The shooting, according to Livingston, appears to have been motivated by gang rivalries between San Francisco and Marin City, though that remains speculative.

One of the five victims in the Halloween shooting, 22-year-old Tiyon Farley of Antioch, was the younger half brother of the sole suspect in a 2015 quadruple murder on Page Street in San Francisco that is also believed to be gang-related.

Related: Two Orinda Shooting Victims Were Armed Rival Gang Members; Party Promoter Held as Accessory

Photo: ATF San Francisco