Update — The U.S. Attorney's Office on Friday announced the arrest of Thaddeus Murphy in connection with the explosion in Colorado Springs in January.
According to the Associated Press, which cited court records filed on Friday, Murphy was distraught over financial problems, and built an improvised explosive device to harm an accountant he said would not return his phone calls and who had not returned his tax records.
Murphy's arrest came after a series of interviews with witnesses who noticed "a specific type of truck" and an individual fleeing the scene, according to a statement from the Department of Justice.
After a monthlong investigation, authorities tracked down a person and vehicle that "closely matched" a description witnesses had given days after the incident. Authorities then obtained a search warrant for Murphy's home, where officers found "seven firearms, and devices similar to the one used at the building," according to the statement.
Because Murphy has prior felony convictions, it is against the law for him to carry firearms. He told police in an earlier round of questioning that the target of his device was not the NAACP.
If Murphy is found guilty of arson, he will be sentenced to at least five years in prison and fined up to $250,000. If he is convicted of being a felon in possession of firearms, he will face as many as 10 years in prison, and another fine of up to $250,000.
Immediately following the January incident, the FBI and Colorado law enforcement officials began searching for a potential person of interest.
Amy Sanders, an FBI spokeswoman in Denver, said in a statement that the blast was caused by an "improvised explosive device" that was placed against the building, which also contains a hair salon.
Sanders said no one was injured in the explosion and there was only minimal damage to the exterior of the building.
She added that a full can of gasoline had been placed near the device, but did not ignite in the explosion.
The FBI is investigating the possibility that the explosion could be an act of domestic terrorism.
"The investigation is still ongoing and it has not yet been determined what the motive was, however domestic terrorism is certainly one possibility among many," Sanders told BuzzFeed News.
Sanders said authorities have identified what she called a "potential person of interest" in the explosion.
She described the individual as a white male believed to be around 40 years old.
Sanders said he is balding and may be driving a "2000 or older model, dirty, white pick-up truck with paneling, a dark colored bed liner, open tailgate, and a missing or covered license plate."
The NAACP chapter’s president, Harry Allen Jr., told The Gazette he would wait for the outcome of the investigation before labeling the explosion a hate crime.
"This won't deter us from doing the job we want to do in the community," he told The Gazette.
The NAACP released a statement saying the cause of the explosion was still unknown. "The NAACP looks forward to a full and thorough investigation into this matter by federal agents and local law enforcement," the statement said.
Sanders added that the FBI's Denver field office is working with the Colorado Springs Police Department at the scene. The Denver Post reported agents from the Bureau of Alcohol, Tobacco, Firearms, and Explosives were also on scene.
Anyone with information was urged to call (303) 435-7787.