A former Boston police officer attacked a fellow cop during the Capitol riot, court docs show, and his old coworker helped ID him

• A former Boston police attacked a US Capitol cop during the riot on January 6, FBI agents allege. 
• Fisher allegedly pushed a chair into an officer and physically assaulted the same officer inside the Capitol. 
• His former coworker helped FBI agents to identify Joseph Fisher using CCTV footage and a drivers license photo. 

A former Boston police officer attacked a fellow cop during the January 6 riot at the US Capitol, the FBI alleged in court documents filed Monday.

According to the documents, the man's former coworker helped the FBI to identify and arrest him. 

The FBI says Joseph Fisher showed up in CCTV footage and YouTube videos wearing a beanie fashioned with the logos of "several Boston sports teams" on the day of the riot, court documents said.

Fisher was seen both outside and inside of the Capitol building, according to court documents.

San Antonio FBI agents provided photos of the man to FBI's Boston office who then matched the images with a Massachusetts driver's license photo of the same man. 

A current Boston police officer who said he'd known Fisher for "more than five years" was able to identify his former coworker from both the FBI images and the driver's license photo, according to court documents. 

Fisher was first identified in a since-removed YouTube video of former President Donald Trump's rally on the morning of January 6 at the National Mall in Washington D.C. 

Screenshots from CCTV footage show Fisher entering the Capitol at approximately 2:24 p.m. through the Senate Wing Door at the North Side of the building, court documents allege. 

Fisher then made his way to the Crypt, then the East Crypt Lobby, before arriving at the Capitol visitor center's Orientation Lobby where an "altercation" broke out between rioters and US Capitol police officers, the FBI alleged.

CCTV footage included in the court documents shows another rioter spraying a "chemical irritant" at police. While a Capitol police officer was running after a rioter, Fisher allegedly pushed a chair into him.  

Fisher then physically assaulted the officer, FBI agents alleged. He exited the Capitol at approximately 2:42 p.m. 

Fisher faces charges of knowingly and unlawfully entering the US Capitol, disrupting government business, and engaging in violence in a restricted government building.