"My girlfriend looked outside and saw him staggering around. There was blood all over, and he was crying," Smith said. "I heard they found his fingers in the back yard."
Streaks of dried blood were still etched across Ferrin's front door yesterday, next to a trio of old mattresses.
Philadelphia police said Ferrin was charged with weapons of mass destruction, risking a catastrophe and related offenses. He hadn't been arraigned because he's still recuperating at Albert Einstein Medical Center.
Special Agent Steve Bartholomew, a spokesman for the Bureau of Alcohol, Tobacco, Firearms and Explosives, said the agency is investigating the incident.
Evidence that was confiscated from Ferrin's house will be tested at an ATF lab, he said.
Bartholomew said the agency is also looking into the possibility that Ferrin has detonated explosives in his neighborhood before.
Sebastian Agudelo, who also lives across the street from Ferrin, said he remembered three other instances.
"They were big explosions. You stopped what you were doing and came outside to see what happened," he said.
"The police came out after one explosion last summer. They drove by, and asked [Ferrin] if he knew what happened. He just said, 'I don't know.' "
Ted Smith claimed that Ferrin once tried to throw an explosive into his house, even though the two seemingly got along well.
"That scared the s--- out of me," he said.
According to court records, Ferrin pleaded guilty in 2011 to a charge of recklessly burning or exploding a property or automobile in Chester County, and received a sentence of five to 23 months in prison.
Fox 29 reported that Ferrin was involved in a grease fire in Florida in 2003 that triggered an explosion after it spread to five pounds of gunpowder.
On a blog called "Doug's Daily Meditation," Ferrin describes himself as a fine artist and painter who also writes songs, essays and fiction.
He shares photos of some of his striking still-life paintings, and riffs on Internet dating and how awful the media treats actress Lindsay Lohan.
"I certainly know what it's like to f--- up big-time; I've been in a few rehabs and once in jail - not for the same reasons, but I know how awful it is to have everyone gossiping about you," read part of one of Ferrin's posts.
"He's a hell of an artist," Smith said, "but I'd say he's got about half a brain. Now he has half a hand."
On Twitter: @dgambacorta