Inside a stately white Colonial, behind a stone wall off Bronson Road close by the rolling grounds of Oaklawn Cemetery, an explosive secret lurked.

The dangerous dimensions of the secret within 1625 Bronson Road, however, were revealed Tuesday night as scores of emergency-services personnel descended on what authorities said was probably the largest personal cache of firearms and ammunition, explosive devices and potentially dangerous chemicals ever uncovered in the town's history.

Nearly 200 firearms -- mostly rifles and long guns -- as well as tens of thousands of rounds of ammunition, a series of devices that had to be disarmed and detonated, and hazardous chemicals, some of them chlorine-based, had been amassed by one man, Joseph C. Callahan, according to police.

Callahan was hospitalized Tuesday afternoon after becoming disoriented. No charges had been filed as of Wednesday afternoon, although police indicated that a warrant is being prepared.

The home at 1625 Bronson Road -- appraised at $1.3 million-- is owned by Callahan and his wife Mary, who is believed to be estranged or divorced from her husband.

But the 69-year-old Callahan, who had a long career history in the arms and chemical fields, appeared to be living alone in the house at the time of the incident. Other than passing pleasantries, he apparently was not well-acquainted with most neighbors or other town residents.

Most, who agreed to talk about Callahan on Wednesday, said they were shocked to learn what authorities found on the property, which required a day-long investigation to seek out and neutralize all the dangerous and potentially hazardous materials.

And they expressed surprise that this "pleasant" and "friendly" man had amassed so much firepower on his property that immediate neighbors were forced to evacuate several hours Tuesday and caused Bronson Road to be closed to traffic in front of the house for a full day.

A chemist and pilot, Callahan is now the owner of the Remair Company, Inc., described as chemist consultants on its website, helping businesses with manufacturing and research processes. A call to the company, which has a Southport postal box, was answered by voice mail Wednesday and the call was not returned. He'd previously worked for DuPont as a research chemist in the 1960s and later held a variety of jobs at Remington Arms, which was owned by DuPont.

On Tuesday night, one neighbor who could not get home because of the Bronson Road closure, described Callahan as a nice guy who was both a gun and rocket enthusiast.

"I'm shocked, I'm totally shocked," former neighbor Melanie Marks said Wednesday. Marks had lived across the street from Callahan until a few years ago. She said she hasn't seen him since she moved.

"He always had a smile on his face, he was thoughtful and helpful," Marks said. "I had no qualms going over there and banging on his door when I locked myself out of the house ... I totally felt comfortable with him."

Stefanie Greenberg lives a few houses down from Callahan on Bronson Road. "I don't know him at all," Greenberg said. "I have no idea who he is."

Greenberg said she was glad she did not know about the cache of weapons and chemicals at Callahan's home last night. "When I heard that there were guns and explosives and he was building explosive devices, I was shocked."

David Faile, president of Friends of Sikorsky Airport, said Callahan is member of that group. He also is a pilot, said Faile, who lives on Cider Mill Road, a short distance from Callahan's home. "I know him, but not very well," Faile said Wednesday. "I've spoken to him several times in the past and knew he lived on Bronson Road."

As for what was found at the Callahan home, Faile said, "In this day and age, nothing surprises me anymore."

Faile said he's sure Callahan still has his pilot's license and that he did fly out of Sikorsky Airport and probably Danbury as well.

A check of Callahan's background found he still has an active third-class pilot's license as of August 2012.

Police have been canvassing neighbors, trying to piece together why Callahan had amassed such a collection at his home, a home they said he has lived in most of his life.

"We don't know his intent," said ATF agent Tim Carroll, while Police Chief Gary MacNamara said, "Anybody who makes bombs has some sort of nefarious reason."

MacNamara said some of the items Callahan had at the home could have been acquired for his hobby of model rockets. "When he crossed the line or why into manufacturing explosive devices, we don't know."

A short distance from Callahan's home, it was business as usual, with most of the business owners and customers unaware Wednesday morning of exactly what had happened to cause Bronson Road to be cordoned off.

"Last night I saw some fire trucks and today there were helicopters overhead and I thought, `OK, they're not doing construction on the road anymore. Something's got to be wrong there,'" said Ed Bocchino, owner of Lexington Home & Garden on Hillside Road, which abuts Bronson.

He said he went online to find out what happened. "I was surprised that someone in Fairfield was doing that," Bocchino said. "Yes, you can say this is definitely out of the realm of normal for this quiet area."

Bocchino said that it's especially scary to think that someone in possession of explosives, weapons and chemicals was living right down the street.

"The way the world is today, your thoughts go immediately to terrorism."

At the Greenfield Liquor Shop on nearby Hillside Road employees said they were stunned to hear the news. "It's pretty amazing what can happen in a small little town," said store manager, Debbie Koulogianis.

At the Greenfield Cleaners on Bronson Road, the owner said he didn't know Callahan, but that his wife, Mary, had an account there until 2009. One woman who entered the store and overheard the conversation with a reporter, said she can't imagine why someone would have such a collection of weapons and explosives at home. "Maybe he was planning a takeover," said the woman, who declined to give her name.