WASHINGTON — The lawyer for a District of Columbia police officer who fatally shot himself nine days after he was injured confronting rioters at the Capitol on Jan. 6 says a group of cybersleuths has identified one of his attackers.

A blow to Officer Jeffrey Smith's head captured on video shows the 12-year veteran being knocked to the ground, apparently unconscious, according to a lawsuit Smith's family filed Friday against the alleged attacker. The lawsuit includes a report from a doctor who evaluated the case for Smith's estate saying a traumatic brain injury led the officer to take his own life.

The family attorney, David Weber, said he turned the name of the potential attacker over to District police, which a department spokesman confirmed.

That spokesman, Dustin Sternbeck, said the agency is "reviewing the information." A spokeswoman for the FBI, which is leading the investigation into the assault on the Capitol, declined to comment.

The Washington Post is not identifying the man named in the lawsuit because The Post could not independently verify his identity and he has not been charged with a crime.

Reached Friday, the man declined to comment. He would not say if he had been to the Capitol on Jan. 6. Social media accounts that appear to be connected to him share conspiracy theories about the election and covid-19 vaccinations.

The HuffPost first reported the sleuthing group Deep State Dogs, whose members scour the Internet trying to identify people involved in the riot, had identified a person possibly involved in the attack on Smith with the help computer images.

"Officer Smith's family has suffered terribly as they mourned amid uncertainty and doubt," said Forrest Rogers, a spokesperson for Deep State Dogs.

Rogers said about a dozen people devoted themselves to identifying Smith's attackers.

Most of that time went toward finding Smith in the crowd, he said, which they did for the first time on Thursday. After that, he said, they quickly identified the man with the help of open-sourced facial recognition software and reviews of photos and videos in which "he wore a distinctive jacket."

Weber's law firm filed a lawsuit in U.S. District Court in Washington claiming wrongful death and assault and battery against one named person and one identified as John Doe. Weber, who is also a forensics professor at Salisbury University in Maryland, said investigators should have worked harder on Smith's case.

"It shouldn't take a forensics professor on summer break to do the government's work," he said.

The lawsuit contains an affidavit from Jonathan L. Arden, one of two doctors who examined the case on behalf of the estate, who concluded the injuries suffered at the Capitol was a "precipitating event that caused that caused the death of Officer Smith."

Smith, 35, shot himself on Jan. 15 while driving his Ford Mustang along with George Washington Memorial Parkway near a scenic overlook on the Potomac River. It was the day after he had been ordered back to work by the Police and Fire Clinic, the first stop for most injured or sick officers seeking treatment.

Capitol Police Officer Howard Liebengood, 51, had taken his life three days after the riot. Two other District officers also took their own lives in July. Their families have not spoken publicly.

Relatives of Smith and Liebengood have said they believe the riot led to the suicides and are pushing for their deaths to be recognized as having occurred in the line of duty.

Earlier this month, relatives of Smith and Liebengood were invited to the White House as Biden awarded the Congressional Gold Medal to officers on the Capitol and D.C. forces who responded to the insurrection. Their participation helped elevate their cause to be included among the list of law enforcement casualties.

Smith's attorney has filed a petition with the District Police and Firefighters Retirement and Relief Board, and he said the new details learned from the video bolster his argument. A line-of-duty death designation would allow his spouse to claim enhanced benefits. That petition is pending.

A therapist who counseled many of the District officers who responded to the riot and led group sessions for hundreds has said she fears many suffered long-term head injuries that have gone undiagnosed.

In interviews with The Post, Erin Smith, the officer's wife, has said her husband became isolated and distraught after returning from the Capitol, refused to walk his dog or go out. She said he couldn't sleep and she would wake to find him crying.

On his police injury form the night of the riot, Smith wrote: "Hit with flying object in face shield and helmet." He added that he "began feeling pain in my neck and face."

Weber said the video found by Deep State Dogs for the first time shows how Smith was injured, and he said it is far more severe than the officer had recalled. He said Smith was not struck by a pole, as he thought, but with a much heavier object the lawyer described as either a crowbar or a heavy walking stick.

Weber said he believes Smith was singled out for attack because the face shield on his helmet was up, exposing his face. Weber said one person passed the stick or crowbar to the second person, who has not yet been identified, who struck Smith in the face. He said the man who hit Smith was wearing padded motorcycle clothing, which the attorney believes was makeshift protective armor.

"You can see Jeff go down," Weber said, adding the officer disappears in the unruly crowd.

He said a Capitol Police officer dragged Smith to safety.

If you or someone you know needs help, call the National Suicide Prevention Lifeline at 800-273-TALK (8255). You can also text a crisis counselor by messaging the Crisis Text Line at 741741.