But Smithee stated that he could not definitively say there was no one else involved. He encouraged witnesses to continue to come forward with information. He said a shotgun has been located as well as a bag with additional ammo near the festival site.
On Monday, authorities executed a search warrant in Mineral County, Nevada, where they said Legan resided before the shooting. Prior to the search, Nevada authorities had no other contact with Legan.
"He appears to have moved into Mineral County this Spring and maintained a low-profile," said Mineral County Sheriff Randy Adams in a statement.
During the Nevada search, authorities collected an empty ammo box, as well as empty rifle boxes. They also collected a bulletproof vest, a camo backpack, hard drives and various tools, such as a pocket knife and a gun light.
Authorities releasing little information about shooter
The FBI said it was continuing to investigate a motive for the attack, as well as looking into the suspect's possible ideology or affiliation with any groups. Multiple media organizations have cited an Instagram account as Legan's, but authorities have not confirmed who owns the account.
Authorities also spent Monday searching a two-story home in Gilroy, said to be Legan's family home, as well as a car parked outside.
A family friend of Legan's, Jerome Turcan, told the Los Angeles Times that when he heard about Sunday's shooting in Gilroy, he called Legan's older brother, Rosino, who was in a car with a cousin searching for his younger brother.
Turcan said they wanted to be sure he was OK and were thinking of going to an emergency room to see if he was there. Turcan said he was shocked to learn the next day that authorities identified Santino as the gunman.
Authorities say witnesses to the shooting can call a hotline at 408-846-0583.
Weapon was purchased in Nevada
In press conferences after the shooting, Smithee talked about the security measures in place at the festival, including areas where attendees were checked with metal detector wands or had their bags searched. But police said that Legan appeared to have gotten access into the festival through a nearby creek and by cutting through a fence.
Authorities said the weapon used by Legan was purchased July 9 in Nevada.
The Associated Press reported that Legan purchased a gun similar to an AK-47 at Big Mike's Guns and Ammo in Nevada, where the legal age limit for purchasing firearms is 18. The age limit is 21 in California.
California Attorney General Xavier Becerra addressed the shooting Monday, saying he believes, based on information currently available, that Legan likely violated numerous state gun laws.
"That weapon could not be sold in California. That weapon cannot be imported into the state of California," Becerra said. "There is a very strong likelihood, as we develop the evidence, that the perpetrator in this particular case violated California law, on top of the crimes of homicide and so forth."