FBI Director James B. Comey said Thursday that investigators were not currently seeking any other suspects in last week's shooting of a Philadelphia police officer by a man who pledged allegiance to the Islamic State.
Comey said authorities had found nothing to suggest that confessed shooter Edward Archer was part of an organized terrorist cell or was planning any follow-up attack.
He downplayed the significance of an anonymous tip police received Saturday that Archer, 30, of Yeadon, might have worked with three other men whose religious beliefs were more radical.
"We're not seeking anybody else," Comey said. "We're going to look very hard to untangle this guy's entire life so we can understand what his motivations might have been."
That said, he added: "We're not done looking."
Comey's comments, delivered during a routine visit to the FBI's Philadelphia field office, came a day after he said the bureau was investigating the crime as a terrorist attack.
The remark made waves in political circles, where debate has raged over how to describe the shooting of Officer Jesse Hartnett, who was ambushed in West Philadelphia and shot repeatedly by a gunman who later told police he acted "in the name of Islam."
But local and federal authorities said Comey's words did not signal a significant shift in the investigation, which had focused on possible terrorism angles from the start.
Comey agreed with that assessment Thursday, though he declined to discuss details of the investigation, including what authorities might have learned about trips Archer took to Saudi Arabia in 2011 and Egypt in 2012.
Though he would not characterize Archer as a "lone wolf" attacker, Comey said people inspired by, if not working with, larger terrorist groups pose the largest terrorism threat to the nation.
"The threat is not Washington-focused. It's not New York-focused," he said. "Wherever there is the Internet and an unmoored soul who might conclude they have to engage in violence to find meaning, there is the nature of the threat."
The ambush was mentioned at Thursday's Republican presidential debate, when Florida Sen. Marco Rubio said, "We are in a war against ISIS. They are trying to attack us here in America. They attacked us in Philadelphia last week."
In response, Lauren Hitt, Mayor Kenney's spokeswoman, reiterated the mayor's position that "the FBI is the only one who can tell us if this is a terrorist attack" and that the agency has not made an official determination.
Earlier in the day, Pennsylvania's two U.S. senators, in separate appearances, decried the shooting.
U.S. Sen. Pat Toomey (R., Pa.) called the attack a clear act of terror. Toomey spoke after meeting with FBI investigators and visiting the injured officer, who remains hospitalized.
Hartnett was shot three times in an arm by Archer, who fired more than a dozen bullets at the officer's patrol car. Hartnett, 33, managed to get out of his car and return fire, wounding his assailant, who was later captured by police.
Archer confessed to the crime and said he did it out of loyalty to ISIS.
Toomey described Archer as "radicalized," but said he had no information about what, if any, connection he had to terrorist groups.
Toomey spoke to reporters after a briefing with William Sweeney, special agent in charge of the FBI's Philadelphia office, on a conference call with Sen. Robert P. Casey Jr. (D., Pa.).
He had few details on the investigation, but he said Sweeney told him "unequivocally they are aware of no other threats that are out there right now." Still, he said, the assault was a "vivid reminder of the dangers the men and women who wear the police uniform around the country face."
"The dangers of radical Islamist terrorism are not limited to countries far away," Toomey said. "It's not just the civil wars that are raging in the Middle East or acts against civilians in Paris and Beirut and Jakarta, but it's attacks against Americans at Fort Hood and San Bernardino - and now Philadelphia."
Later Thursday, Casey, who joined Police Commissioner Richard Ross and Kenney at a news conference, struck a similar note. He said terrorist attacks across the country underscored the need for federal and local law enforcement officials to work together on these kinds of investigations. To adapt to the rise of small-scale attacks by people inspired by ISIS, he said, local law enforcement agencies should become more actively involved in the search for terrorists.
These isolated attackers, he said, are "a kind of practice . . . we have to assume will happen again, we have to be ready for."
Ross said Hartnett, whom he called a brave and compassionate officer, had sustained "significant damage" to his arm and faced a lengthy recovery.
Kenney has said from the start that Archer's crime was not a reflection on Islam, and stood by those comments.
"Basically, what I said was, 200,000 Muslims who live in Philadelphia are not represented by the actions of Mr. Archer. That he's a criminal and they are not criminals," Kenney said.
So while federal authorities say they are investigating the shooting as act of terrorism, Kenney said he would wait for that work to conclude before characterizing the crime. "I don't think speculation is effective," he said. "We have to wait and see what the FBI and Philadelphia Police Department discover as a result of their investigation. Speculation is what's made this thing run wild, scaring people and putting people at risk."
Contributing to this article were staff writers Julia Terruso, Dylan Purcell, Robert Moran, and Thomas Fitzgerald.