https://www.washingtonpost.com/news/fact-checker/wp/2015/12/10/marco-rubios-claim-that-no-recent-mass-shootings-would-have-been-prevented-by-gun-laws/

Dec. 2, 2015: Syed Farook and Tashfeen Malik killed 14 people in San Bernardino, Calif., using a Smith & Wesson M&P AR-15 type rifle, a DPMS Panther Arms AR-15 type rifle, a Smith & Wesson semiautomatic pistol and a Llama semiautomatic pistol. The guns were purchased legally and the rifles were purchased legally by a former neighbor. Four high-capacity magazines were found, perhaps holding as many as 30 rounds.

Analysis: California has some of the strictest gun laws in the nation, dating from 1989, and specific types of AR-15 and AK-47 style rifles are banned. Ammunition magazines that hold more than 10 bullets are also outlawed, though older, larger magazines are grandfathered. A proposals to pass a federal version of California’s law was defeated in the Senate in 2013. There are indications that the suspects illegally modified their California-compliant weapons. In any case, the laws did not thwart them. (Gov. Jerry Brown, a Democrat, in 2013 vetoed a bill that would have toughened the law, but the guns used in the attack were purchased before the law would have taken effect.)

Oct. 1, 2015: Christopher Harper-Mercer killed nine people at Umpqua Community College in Oregon. He owned 14 firearms and conducted the attack with six of them, including a Glock pistol, a Smith & Wesson pistol, a Taurus pistol and a Del-Ton AR-15 rifle. All were purchased legally.

 Analysis: No proposed laws would have prevented these purchases.