A Foster City man was arrested last week after investigators found evidence he had fit a gun with a grenade launcher, Contra Costa County sheriff’s officials said Monday.
Joseph Holmes, 41, was taken into custody on Thursday after crews with the Contra Costa County Anti-Violence Support Effort (CASE) found illegal firearms, some of which had been modified, in his home. Earlier in the year, CASE received a tip that a person had obtained Glock conversion switches, which let pistols fire in automatic mode, according to the sheriff’s office.
CASE’s investigation led them to Holmes’ residence, where they found multiple Glock switches, assault pistols and rifles, ammunition and a machine gun with a silencer and grenade launcher attached, sheriff’s officials said.
Holmes’ case will be passed to the Contra Costa County District Attorney’s Office for prosecution, according to the sheriff’s office. CASE was created in November 2011 as a collaborative effort to reduce violent crimes in the county, especially those related to illegal firearms.