Expanded Background Checks Failed to Stop California Jihad

From Breitbart's Big Government:

When Syed Farook and Tashfeen Malik carried out their California jihad on December 2, they did so in a state with expanded background checks, registration requirements for “assault weapons,” and an “A-” grade from the Brady Campaign to Prevent Gun Violence.

None of these things prevented the attack from occurring. Gun Violence.

California has expanded background checks, which means they require a background check on every sale–retail or private. These are the very checks that President Obama, Senator Joe Manchin (D-WV), and Democrat surrogates like Gabby Giffords, Mark Kelly, Shannon Watts, and others are pushing at the federal level on the false premise of keeping Americans safe. They are the same checks that Colorado enacted after the heinous December 2012 attack on Sandy Hook Elementary, under the illusion that such checks would prevent a high profile public attack.

All of the laws that the gun control proponents want to pass nationally are in effect in California, yet we still have mass shootings.

How can that be? Ask and gun control proponent to explain why the laws they want DIDN'T work in California?