PHILADELPHIA (Reuters) – Police were out in large numbers on Monday in the Philadelphia neighborhood where a man inspired by Islamic State militants last week shot a police officer, with officials investigating a tip that the gunman may have been part of a larger group.

Police said on Sunday that a man stopped officers patrolling near the site of the attack and warned that suspected gunman Edward Archer, 30, had been part of a group of four men who may pose a danger to police. But a federal law enforcement official, speaking on condition of anonymity, on Monday cautioned that it was not clear how credible that threat was.

Archer, who friends said worked in construction and went by the Muslim name Abdul Shaheed, lived in Yeadon, a suburban town just over the Philadelphia border. He appeared to maintain roots in West Philadelphia, and stayed at times in a vacant home owned by a relative, near the mosque where he worshipped and just two blocks from the scene of an attack that police have called an ambush.

In an attack caught on video, a gunman police say was Archer was seen shooting into a patrol car driven by Officer Jesse Hartnett, 33, who was shot in the arm but managed to fire back. Archer, who sustained a bullet wound to the buttocks, was arrested at the scene and charged with attempted murder.

Archer, police say, told them that the attack was done “in the name of Islam.”

On Monday morning multiple police cruisers, including one SWAT unit and two units assigned to the department’s counter-terrorism unit, could be seen in the neighborhood.

Jacob Bender, the director of the Philadelphia chapter of the Council for American Islamic relations said that local leaders, wary of the increased scrutiny that acts of violence brings on the community, are quick to report threats of violence.

“People running around shooting police cars is the last thing the community wants,” Bender said.

(Editing by Scott Malone and Andrew Hay)