Peter Bergen is CNN's national security analyst, a vice president at New America and a professor of practice at Arizona State University. He is the author of " United States of Jihad: Investigating America's Homegrown Terrorists ." David Sterman is a policy analyst at New America's International Security Program

(CNN) The violence this week on the campus of the Ohio State University has, like previous attacks before it, provoked an outcry of fear and calls for greater security measures to protect Americans against terrorism. And yet, like other incidents before it, this attack was carried out by a terrorist whose inspiration to act reportedly came from within, not beyond, America's national borders.

In a message that Artan is believed to have posted on Facebook minutes before the attack, he urged readers to "listen ... to our hero Imam Anwar al-Awlaki."

Awlaki was a Yemeni-American cleric who left the United States in 2002 and who eventually joined al Qaeda in the Arabian Peninsula in Yemen, where he was killed in a CIA drone strike in 2011. He has continued to exert influence after his death, via a variety of videos and manifestos that are widely available on the Internet.

Since Artan's attack, some have speculated his radicalization took place overseas. Republicans like Sen. Rand Paul of Kentucky pointed to the attack as justification for placing further restrictions on resettling refugees from 33 countries designated "high-risk," including Somalia.

Yet, in key ways, regardless of where Artan was radicalized, his attack has its roots in the United States, because his spiritual mentor was Awlaki, a US citizen born in Las Cruces, New Mexico, in 1971 while his Yemeni father was studying at New Mexico State University. Awlaki himself was aware that Americans could be influenced by his ideas, writing , "Jihad is becoming as American as apple pie."

Six years after Awlaki was born, his family moved back to Yemen, but he returned to the States for college and remained for much of his adult life. As an undergrad, Awlaki attended Colorado State to study engineering. In 1995, he moved to San Diego, where he took up a job as a cleric. By early spring 2002, Awlaki was studying in a doctoral program at George Washington University, but he left the country after learning the FBI was investigating him.

First Awlaki traveled to London and then to Yemen. In 2006, he was thrown into a Yemeni jail. Awlaki characterized this as the result of his intervention into one of Yemen's numerous, and often deadly, tribal disputes. The US government asserted that his imprisonment, in fact, came after Awlaki became involved in an al Qaeda plot to kidnap a US official.

By the time Awlaki secured his release, he was becoming the key cleric in the English-speaking world of radical Islam, one that militants were turning to for answers and one who exerted enormous spiritual power on militants living in the United States.

What made (and continues to make) Awlaki's propaganda so successful was the way he drew upon Western and American history to illustrate his religious justification. In one propaganda piece, Awlaki emphasized his Americaness , stating, "I for one, was born in the US, I lived in the US for 21 years. America was my home." He then proceeds to argue that America is at war with all of Islam, including American Muslims.

Awlaki's message has resonated with some of the more infamous perpetrators of terrorism in the States.

Maj. Nidal Hasan, for instance, an American of Palestinian descent born in Virginia, killed 13 people at Fort Hood, Texas, in 2009 after sending 18 emails to Awlaki in Yemen, a correspondence that was known to the FBI. Awlaki did not direct the attack, but he was the key inspiration for Hasan.

Carlos Bledsoe, an African-American convert to Islam, shot up an Army recruiting center in Little Rock, Arkansas, killing an American soldier in 2009. After the attacks, Bledsoe said his spiritual inspiration was Awlaki.

Awlaki was also an influence on the two Tsarnaev brothers, who killed three people in the Boston Marathon bombings in 2013. At the time of the bombing, Dzhokhar Tsarnaev was a naturalized American citizen and Tamerlan Tsarnaev was a legal permanent resident seeking citizenship. Both brothers were younger than 10 when they entered the United States; their radicalization occurred in America.

Even in death Awlaki's message has resonated with American militants. New America has found more than 60 jihadist terrorism cases in the States since Awlaki was killed in which he influenced the perpetrators, who are a broad range of American men and women hailing from multiple ethnic groups from across the United States.

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Among those influenced by Awlaki after his death was Omar Mateen , who killed 49 people in the deadliest terrorist attack in the United States since 9/11 in Orlando, Florida, in June.

And now we have Abdul Razak Ali Artan, a Somali teenager from Ohio.

The continued attacks in Awlaki's name more than five years after his death demonstrate that the United States will be dealing with jihadist violence inspired by this American citizen for years to come.