Ian David Long shot 12 people inside a Thousand Oaks, California bar and used an illegal extended magazine, police said.
Ian David Long, the man police say shot 12 people inside a Thousand Oaks, California college bar before dying of his own wounds, used an illegal extended magazine that allowed his gun to hold more bullets as he waged a gunfight and standoff with police that lasted over an hour, police said.
Witnesses to the shooting reported hearing at least a dozen shots while fleeing the bar. A police spokesman said that authorities responded to a call of shots fired and showed up around three minutes later and still heard shots going off.
Ventura County deputy sheriff Sgt. Ron Helus rushed into the bar while shots were still going off and was struck "multiple times by gunfire," according to police. Helus, along with 11 others, later died of his wounds.
The Thousand Oaks shooting will go down as tied for the 15th deadliest US shooting on record, but unlike the Las Vegas shooting, which affected many of the exact same people, only one commonly available handgun was used.
Police at the scene found just one handgun, Sheriff Geoff Dean, who responded to the incident, told the "Today" show.
When asked on the show if he thought it was unusual "that a handgun could cause that much damage that quickly," Dean said he wasn't surprised.
"Assault rifles get all the attention but certainly a handgun in the hand of the right person can certainly wreak a lot of damage, especially at close range."
Long, a veteran of the Marine Corps, would have had training with firearms. Long used a Glock .45, which fires one of the largest-caliber bullets commercially available.
The factory-standard magazine on Long's Glock likely held 13 rounds, and the gun can accommodate another round loaded into the chamber and ready to fire.
But Long had an extended magazine, according to police. Extended magazines available for sale on the Long's model of Glock can hold 21, 30 or more rounds.
California has passed a series of laws outlawing the sale of extended magazines, which they consider "any ammunition feeding device with the capacity to accept more than ten rounds" in calibers above .22.
California 3rd District Congressman John Garamendi, who during his time as a California state legislature wrote some of the state's current gun laws, told INSIDER that Long's magazine was "obviously illegal."
"That particular magazine that he had cannot be possessed in California, let alone sold," said Garamendi.
Previously, California had allowed guns with larger-capacity magazines to be grandfathered in if they were lawfully obtained before 2000, but in 2016, California voters passed Proposition 63, which outlaws the very possession of such magazines.
But some of the country's toughest gun control laws still haven't stopped mass shootings in California.
"Interstate activity is a major concern," said Garamendi, pointing out that Long could have bought his gun elsewhere and brought it to California.
Garamendi, recently re-elected to his seat as part of the House of Representatives new Democratic majority said he supported a nationwide ban on extended clips.
While most gun legislation revolves around long guns, which often accommodate magazines with more than ten rounds, the wide majority of all gun violence happens with pistols like the one Long used.
A Glock like Long's is less than eight inches in length or height, just about two inches across, about a pound and a half in weight, and can be easily concealed on one's person.