EDITOR’S NOTE: An earlier video version of this story incorrectly reported that the so-called ‘bullet button’ could change a weapon from being semi-automatic. We regret the error.
Two handguns and two rifles -- all legally purchased in California.
Those were the weapons FBI investigators say Syed Farook and wife Tashfeen Malik used to kill 14 and injure 21 people last week in San Bernadino.
Authorities said at least 75 rounds were shot by what looked at first to be illegal assault rifles. But one small detail made them legal.
"California in theory has an assault weapons ban. But that has been subverted by the gun industry with what they call the 'bullet button,'" Dr. Bill Durston, President of Sacramento Physicians for Social Responsibility said.
Dr. Durston is an expert Marine marksman and a retired emergency physician.
"I've seen too many victims of gun violence in my career," he said.
Unlike any other state, in California, rifles must have a fixed magazine. This means, a shooter cannot easily remove a magazine with no more than 10 rounds, with just a push of a button. Instead, they must use a tool to exchange magazines. This "bullet button" allows for that.
Rob Adams is the owner of Sacramento Black Rifle in Rocklin. His store is also licensed to sell assault weapons for law enforcement and others. He showed FOX40 the difference between a legal rifle and an assault weapon banned in California.
"You need a tool to push this [bullet] button to release the magazine," Adams said.
If trained, a person can use the bullet button to swap out magazines in a matter of seconds. And it is perfectly legal because the magazine is technically fixed. If it was not fixed, it would be illegal.
"Ingenuity is what is it," Adams said. "This was created specifically for California."
Anti gun advocates call this specially made-for-California component a gun law loophole.
"The solution is ban the handguns with no grandfather clause. Ban all rapid fire semi-automatic rifles and pump action shotguns," Dr. Durston said.
In 2013, California’s legislature passed a bill that would have outlawed all semi-automatic rifles that had the capacity to accept detachable magazines, including guns equipped with bullet buttons, but Governor Jerry Brown vetoed the measure, saying it and other proposed gun control measures went too far in their restrictions.