But as tips have poured in and charges have mounted against rioters who stormed the legislative building on January 6, the identity of the would-be bomber remains a mystery and one of the most troubling avenues of the massive federal investigation.
“They could potentially be building more bombs right now,” said Ashan Benedict, the special agent in charge of the Washington Field Division of the Bureau of Alcohol, Tobacco, Firearms and Explosives, in an interview Wednesday.
“This person obviously knows who he or she is, they may have told their story to someone else, and in the face of humanity, the fact that a lot of people could have been hurt if this device went off should be enough for someone to come forward so it doesn’t happen again,” he said.
Investigators are considering the possibility that the devices were part of a plan to divert law enforcement resources away from the Capitol as rioters began to force their way in.
As of Wednesday, more than 150 people have been charged by federal prosecutors in connection with the riots.
Officers from the Bureau of Alcohol, Tobacco, Firearms and Explosives, FBI, US Capitol Police and DC Metropolitan Police had responded to the scene at the two offices, which are less than a quarter mile apart and just blocks south of the Capitol.
The bombs were discovered within minutes of each other around 1 p.m. ET on January 6, just around the time that a mob of angry supporters of President Donald Trump descended on the building after a nearby rally with the President, according to an account the acting chief of the US Capitol gave to lawmakers Tuesday and a “seeking information” poster publicized by the FBI.
Eight inches long and made of galvanized steel, according to a law enforcement official, the devices were placed out in the open. One, by the offices of the Republican National Committee, was discovered by a 36-year-old on her way back from putting in a load of laundry.
Benedict wouldn’t offer a description of the devices or say what materials they contained, but a law enforcement official familiar with the matter said they contained an explosive powder and were set to go off via the timer.
It’s still unknown why the devices did not explode, the official said. One theory under investigation is that the timers were set incorrectly. Another is that the batteries may have been improperly connected, the official said.
As part of their examination, investigators have cross-referenced the components of the pipe bombs in a database of other explosive devices that’s composed of contributions from bomb squads across the country. That process has been helpful, according to Benedict, who noted that the devices appear to have been built using traditional components that are not unique, and are similar to other pipe bombs that law enforcement has encountered in the past.
At the same time, investigators are imploring the public to phone in any information they may have about the bomber, and to share any pictures or videos they recorded at the scenes.
Agents have canvassed the areas where the devices were found and pulled hours of surveillance footage. Authorities have also received cellphone location data in the vicinity of the two offices in the hours ahead of the bombs’ discovery to try to narrow down the number of possible suspects, according to law enforcement officials.
A photo of the person believed to have planted the bombs, taken from surveillance images, has been widely shared by law enforcement.
In the photos, the person appears in a gray hooded sweatshirt and is carrying a backpack. One photo shows a close-up of the person’s shoe, which has a distinctive pattern.
“Everything that this individual is wearing is a potential clue,” Benedict said. “Every piece of clothing, every piece of headware potentially could be unique to help us trace back this individual to their origin.”
When the first report of a bomb came into the ATF through DC’s Metropolitan Police Department, Benedict and his top deputy got in a car and drove to the scene, something he says he only does in the most serious cases.
“It was probably one of the most stressful environments that I’ve been around,” Benedict said.
“While we’re standing there at this bomb scene, the radios from the uniformed officers I’m speaking with are going off in greater intensity. It’s not just your normal radio transmissions — folks are calling for help and their voices are raised,” he said.
CNN’s Evan Perez contributed to this report.