Fairfield resident Ryan Estes, who was identified as a drug dealer during the trials of Gene Combs and Henry Don Williams, was booked into the Solano County jail with the six others who were arrested.
Estes was reportedly Combs' and Williams' intended target when Garcia was shot in 2008.
During Monday's sting operation, police used decoys between 17 and 19 years old to contact 45 people outside licensed businesses in Fairfield.
Estes, two other Fairfield residents, three Fairfield transients and an American Canyon resident also were arrested, police said.
Testimony at the trials of 46-year-old Combs and 33-year-old Williams, which ended earlier this month, revealed the pair went to Estes' Cordelia residence on Sept. 1, 2008, to collect money Estes owed Combs for a drug transaction.
Estes wasn't home, and as Combs and Williams left the neighborhood, 22-year-old Garcia arrived in a Cadillac to visit a friend, according to the trial testimony.
Williams mistook Garcia for Estes and shot Garcia once in the head, according to the testimony. Garcia died after his family donated his organs.
Combs and Williams are scheduled to be sentenced July 19.