A group of students and teachers protested outside of the White House Monday afternoon, demanding a call for action on gun control. The “lie-in” featured 17 Washington D.C. students lying on the ground, representing the students that were killed in last week’s mass shooting at Marjory Stoneman Douglas High School in Parkland, Florida.

Teens for Gun Reform is the name of the group that organized the protest. They said the demonstration lasted three minutes to represent how long it took suspected shooter Nikolas Cruz to purchase the AR-15 he allegedly used on Feb. 14.

“We have organized this protest in solidarity with all of those who were affected by the horrific school shooting in Florida last Wednesday,” the organization said in a statement. “We call on President Trump and leaders from both parties to finally act in the interest of America’s youth and end these tragic mass shootings! It is imperative that American children are safe in their classrooms, churches, malls, movie theaters and streets!”

“Am I Next?,” “Make our Schools, Churches, Playgrounds Safe Again,” and “NRA, There is Blood on Your Hands” were among the signs that protesters were holding during the lie-in. Another student held a sign that listed the cities and death tolls of recent mass shootings in the United States.

The gun that was allegedly used in the school shooting was bought legally by Cruz about a year ago at Sunrise Tactical Supply in Florida. Attorneys for the store’s owner said there were no red flags when Cruz provided his identification and background information in order to make the purchase, according to NBC News.

The FBI received a tip about Cruz on Jan. 5 regarding his “gun ownership, desire to kill people, erratic behavior, and disturbing social media posts, as well as the potential of him conducting a school shooting.” The family that took Cruz in nearly three months ago when his adopted mother died said the suspect seemed “normal” and didn’t show any signs of being a potential mass shooter.

Principal Deputy Press Secretary Raj Shah said in a statement Monday that President Trump is “supportive of efforts to improve the federal background check system.”