Call to Jihad
In an audio message released earlier in the year, Daesh spokesperson Abu Muhammad Adnani told the group’s supporters to carry out attacks in their home countries, saying the "smallest action you do in [the West] is better and more enduring" than fighting on Daesh territory. It was not the only such message but a vivid illustration of what was driving lone actors to engage in terror inside the United States.
US officials had warned that the group would try to strike outside of Syria and Iraq as it lost territory in those countries.
In July, National Counterterrorism Center Director Nicholas Rasmussen testified before the US Congress that the potential for homegrown violent extremism had grown significantly in the past few years. He warned that the United States should expect domestic terrorists to capitalize on the media attention given recent attacks in the country.
Rasmussen’s comments came amid a series of terror attacks against police officers and civilians, including the deadliest terrorist attack on US soil since September 11, 2001, indicating that adherents to the radical Islamist ideology embraced the call to arms to strike out at home.
The terror attacks carried out on US soil in 2016 were perpetrated by lone actors who either claimed or are suspected to be inspired by overseas terrorist organizations, including the Islamic State and al-Qaeda.
The suspects were all US-born or had immigrated with their families, and none of them had been found to have direct ties to foreign terror groups. The five attacks killed 50 people and injured 97 others, including four police officers.
Philadelphia police officer ambushed
The first terror attack of 2016 began around 11:40 p.m. on January 8 when Edward Archer fired 13 shots at the moving patrol car of Philadelphia police officer Jesse Hartnett, hitting him three times in the left arm.
Despite suffering significant damage to his arm, Hartnett managed to leave his car, fire his weapon and chase his assailant before other police officers apprehended Archer a few blocks away.
Police Cpt. James Clark told reporters that 30-year old Archer repeatedly pledged allegiance to the Islamic State. "He kept on echoing those sentiments and wouldn’t give us anything more than that," Clark said at a news conference following the attack.
Archer further said he targeted a police officer because they enforce laws that are contrary to his interpretation of Islam, according to Philadelphia Police Commissioner Richard Ross.
The FBI later said Archer traveled to Saudi Arabia twice in 2011 and to Egypt for several months in 2012 but did not publicly connect the trips to the attack.
FBI Director James Comey said there was no evidence Archer had ties to international terrorist organizations despite his claimed allegiance to Daesh.
Archer’s defense attorneys have suggested he may be mentally impaired; his mother said Archer sustained head injuries from football and an accident and that he was hearing voices prior to the attack.
In May, Philadelphia prosecutors charged Archer with attempted murder, aggravated assault and assault of a law enforcement officer. His trial is expected to begin in June 2017.
Ohio restaurant attack
On February 11, barely a month after the Philadelphia shooting, Mohamed Barry attacked patrons inside the Nazareth restaurant in Columbus, Ohio with a machete. Barry injured three customers before fleeing the scene.
Police chased Barry’s car for about five miles before catching up with him and forcing him off the road. Columbus Police Sgt. Rich Weiner said Barry then lunged across the police car with the machete and a knife, prompting officers to shoot and kill him at the scene.
The 30-year old Barry was born in Guinea and had lived in the United States for 16 years.
Weiner later said a computer alert about Barry and his vehicle prompted police to call federal law enforcement and a counter-terror task force after the attack.
Four years before the attack, the FBI investigated Barry for making "radical statements," according to media reports, but no charges were filed.
Orlando Pulse nightclub shooting
On June 12, Omar Mateen launched the deadliest attack in the United States since September 11 and the worst mass shooting in the country’s history, shooting nearly 100 people he had taken hostage inside the Pulse nightclub in Orlando, Florida, which caters to the city’s lesbian, gay, bisexual and transgender (LGBT) community.
The 29-year old native of Afghanistan killed 49 people and left another 50 wounded over the course of several hours before police stormed the club and shot and killed him.
During the incident, Matten spoke with police by phone and said he was acting in the name of Daesh.
Mateen further said he was retaliating for the May 2016 killing of a senior Islamic State commander, Abu Wahib, in a US airstrike in Iraq.
In July, Central Intelligence Agency director John Brennan said the agency did not undercover any direct connection between Mateen and foreign terrorist organizations.
The FBI investigated Mateen in 2013 after he told co-workers that his family had connections to both al-Qaeda and Hezbollah. However, the two groups are enemies of each other as well as Daesh.
Despite media reports that Mateen targeted the club because he struggled with his own sexual orientation, Attorney General Loretta Lynch said investigators may never be able to narrow down Mateen's actions to one motivation.
Speaking in Orlando after the shooting, she described the attack as both an act of terrorism and an act of hate against the LGBT community.
The attack renewed calls by US lawmakers to tighten the country’s gun laws, but compromise legislation failed to pass in both the Senate and House of Representatives.
Bombings across New York and New Jersey
Early on September 17, a bomb exploded in a trash can near a US Marine Corps charity race in the beach city of Seaside Park, New Jersey, about 80 miles south of New York. Police in New Jersey said the improvised explosive device contained three pipe bombs that had been strapped together, but only the center bomb detonated.
Eleven hours later, on Saturday night, an explosion in the Chelsea neighborhood of Manhattan injured 29 people. A second device was later discovered in a discarded trash bag on West 27th Street, four blocks from the blast.
Two police officers later confronted 28-year old Ahmad Khan Rahimi in nearby Linden after someone reported a man asleep in the doorway of a bar. One of the responding officers recognized Rahami, Linden police captain James Sarnicki explained.
Rahami opened fire on police, striking one officer in his bulletproof vest. A second officer was injured by broken glass, Union County, New Jersey Prosecutor Grace Park told a news conference. Neither officer was critically injured.
Rahami sustained at least one gunshot wound in the leg during the incident and underwent surgery in Newark.
In 2014, the Afghan native was arrested on weapons and assault charges, according to court documents. FBI Director Comey said there was no indication Rahimi operated as part of a larger terror cell. In an interview, Rahimi's father told US media that he warned the FBI in 2014 that his son was a terrorist.
According to reports, Rahami Sr. was prompted to contact the officers after his son had had a fight with another of his sons and stabbed the man.
In December, a US federal court indicted Rahimi on eight counts in connection with a series of bombings carried out in New Jersey and New York earlier this year. A New Jersey court earlier charged Rahimi with five counts of attempted murder of a police officer and weapons violations in connection with the September 17-19 bombings. On December 20, Rahimi plead not guilty.
Ohio State University attack
On November 28, Ohio State University student Abdul Razak Ali Artan drove onto campus in Columbus and rammed fellow students with his car before attacking others with a knife.
Artan was identified as an 18-year old refugee from Somalia who moved to the United States in 2014 and obtained US permanent residency.
Daesh claimed responsibility for the attack, saying on its Amaq news agency that Artan was a "soldier of the Islamic State" retaliating for US-led coalition military actions in Iraq and Syria.
Two days before the attack, the Islamic State released a propaganda video encouraging supporters not to use firearms to carry out attacks in the west. The video specifically encouraged the use of knives and gave instructions on how to make small bombs.
FBI Special Agent Angela Byers told reporters it was too early to determine if the claim was valid but said the Joint Terrorism Task Force was investigating the attack.
Police later said Artan had written posts on Facebook condemning US interference in foreign countries and said he was "sick and tired" of attacks on Muslims. According to media reports, he referenced the Daesh and Anwar al-Awlaki, a deceased US-born cleric linked to al-Qaeda in Yemen.
The Obama administration has repeatedly called for tighter gun control laws to prevent terrorists from getting their hands on guns, but Congress has failed to take any measures to address the issues. Others have called for stronger efforts to counter violent extremism and a crackdown of how extremists groups use social media to influence and recruit followers.