PHILADELPHIA (CBS) — The FBI has joined Philadelphia Police in investigating a possible new threat against officers.

The disturbing tip came days after the ambush of Officer Jesse Hartnett.

Nearly four days after video shows a suspect ambushing and wounding 33-year-old Hartnett inside his patrol car near 60th and Spruce streets, Police Commissioner Richard Ross told Eyewitness News reporter Walt Hunter that investigators still are trying to determine if the alleged actions of 30-year-old Edward Archer could be part of a wider threat against police.

“I just off the phone with the agent in charge of the FBI and he gave me an update that’s pretty much status quo, but they are looking to put their hands on some folks just to talk to them,” Ross told Eyewitness News.

The new concerns first raised Saturday when officers near the shooting team were told by an anonymous informant that the “threat is not over” and that accused attacker Archer was “part of a group of three others and is not the most radical of the four.”

As a precaution, heavily armed SWAT teams now patrol near the shooting scene.

Officers citywide were ordered to double up and are not riding alone until police learn more.

“We have to do it, in light of the information we received yesterday. We’d be remiss if we didn’t look at that. We still don’t know if there is anything more involved,” the commissioner said.

Meanwhile, police, friends and family maintain a constant vigil at the wounded officers bedside.

“Some people might be thinking he was shot in the arm. It’s far more serious than that. His healing is pretty complex,” Commissioner Ross explained.