Nikolas Cruz, the troubled 19-year-old suspected of killing 17 and injuring over a dozen in a shooting spree at Marjory Stoneman Douglas High School in Parkville, Florida, legally purchased the AR-15 rifle he allegedly used in the crime.
The AR-15 is one of the most popular semi-automatic rifles in the US.
More on the AR-15
AR-15 assault rifle
AR-15 assault rifle
AR-15 rifles are displayed on the exhibit floor during the National Rifle Association (NRA) annual meeting in Louisville, Kentucky, U.S., on Friday, May 20, 2016. The nation's largest gun lobby, the NRA has been a political force in elections since at least 1994, turning out its supporters for candidates who back expanding access to guns. Photographer: Luke Sharrett/Bloomberg via Getty Images
AR-15 rifles are displayed at the SIG Sauer GmbH booth on the exhibit floor during the National Rifle Association (NRA) annual meeting in Louisville, Kentucky, U.S., on Friday, May 20, 2016. The nation's largest gun lobby, the NRA has been a political force in elections since at least 1994, turning out its supporters for candidates who back expanding access to guns. Photographer: Luke Sharrett/Bloomberg via Getty Images
Civilian legal AR-15 rifles are displayed for sale at a vendor's booth during the Fall 2015 Knob Creek Machine Gun Shoot in West Point, KY, U.S., on Friday, Oct. 9, 2015. The Machine Gun Shoot is a three day bi-annual event that attracts gun dealers, collectors, and enthusiasts from all across America in what is considered one of the largest gun shows in the world dealing specifically with high caliber weaponry. Photographer: Luke Sharrett/Bloomberg via Getty Images
This February 4, 2013 photo illustration in Manassas, Virginia, shows a man holding a Colt AR-15 semi-automatic rifle. US President Barack Obama Monday heaped pressure on Congress for action 'soon' on curbing gun violence. Obama made a pragmatic case for legislation on the contentious issue, arguing that just because political leaders could not save every life, they should at least try to save some victims of rampant gun crime. AFP PHOTO/Karen BLEIER (Photo credit should read KAREN BLEIER/AFP/Getty Images)
POMPANO BEACH, FL - JANUARY 16: An AR-15 is seen for sale on the wall at the National Armory gun store on January 16, 2013 in Pompano Beach, Florida. President Barack Obama today in Washington, DC announced a broad range of gun initiatives that his administration thinks will help curb gun violence. (Photo by Joe Raedle/Getty Images)
MIAMI, FL - DECEMBER 18: In this photo illustration a Rock River Arms AR-15 rifle is seen on December 18, 2012 in Miami, Florida. The weapon is similar in style to the Bushmaster AR-15 rifle that was used during a massacre at an elementary school in Newtown, Connecticut. Firearm sales have surged recently as speculation of stricter gun laws and a re-instatement of the assault weapons ban following the mass shooting. (Photo illustration by Joe Raedle/Getty Images)
AURORA, CO - JULY 22: A Bush Master AR15 assault rifle is displayed at Firing-Line July 22, 2012 in Aurora, Colorado. Firing-Line is located not far from where suspect gunman James Eagan Holmes, 24, is accused of killing 12 people at a screening of the new 'Batman' film last Friday. The firearm is similar to the one used in the rampage. (Photo by Joshua Lott/Getty Images)
Sen. Bill Nelson of Florida said law enforcement officials had briefed him on Cruz, and that Cruz had undertaken "enormous preparation" for the shooting and was equipped with a gas mask and smoke grenades. Gas masks and smoke grenades are typically also legal for purchase with few restirctions around the US.
At 19 and without a criminal background and as a US citizen — despite Cruz's disciplinary record at school — all he needed was a few hundred dollars to buy the rifle.