He had released his estranged wife, Deborah Trumpower, at about 10:30 a.m.
Mades said the standoff began after police received a call at 4:45 a.m. from a man inside Hadley Farms bakery, where Deborah Trumpower works.
Within minutes, three deputies entered the Main Street building and started talking with David Trumpower, 46, who was holding a sawed-off shotgun on his estranged wife.
At 9:15 a.m., Deputy Bill Blair radioed out that David Trumpower was sitting in a chair with the shotgun pointing to the floor and his wife sitting nearby, Mades said.
Michael Price, described as a friend of Deborah Trumpower, hid in the building until David Trumpower was arrested, Mades said.
David Trumpower's desire to see his sister, Cheryl D. Metzer, and his children, Kimberly and Brent Trumpower, helped resolve the situation, Mades said.
"We told him we would let him talk to them if he laid down the shotgun," Mades said.
Metzer, who arrived at about 9 a.m., said in a telephone interview Tuesday afternoon that she talked to her brother in an attempt to keep him from killing himself.
"I had to give him hope to live for, his children and myself," she said.
"I told him that I loved him, and I told him to come out and give me a hug because I needed one and I wanted to give him one," she said, breaking into tears.
When David Trumpower put the gun down and began walking toward the negotiators, other officers got between him and the gun, Mades said.
David Trumpower was charged with first- and second-degree assault, reckless endangerment, false imprisonment and criminal trespass, Mades said.
He also faces two weapons charges, including carrying a shotgun with intent to injure and having an illegally-shortened shotgun, Mades said.
Mades said the situation was tense for a time, and expressed relief at the way it ended.
"If it's a matter of shooting the guy we could have shot him three or four times," Mades said. "That decision would be mine to make. Thank God I didn't need to make it."
Before Trumpower surrendered, Mades said the man didn't want to go to jail or receive psychiatric treatment.
"He doesn't want to face what he's going to face when he comes out."
Trumpower was jailed previously for violating a Feb. 25 protection order filed by Deborah Trumpower, according to court records.
"It's a classic case of domestic violence," Mades said.
Metzer said the judicial system failed her brother. She had twice sought emergency psychiatric treatment for him through the courts.
In March, he was taken to the hospital for about a week of treatment, she said. In September, the judge told her there was nothing he could do until her brother did something, she said. Metzer said he needed six months, not a week, of treatment.
Metzer said the negotiating team promised her they wouldn't just throw him in jail and forget about him.
Mades described the tense standoff as "a truly cooperative effort" between the deputies and the Maryland State Police, with men and equipment coming from as far away as Jessup.
A state police special response team carrying M-16 rifles, a negotiating team and specialized equipment including a camouflaged vehicle with a battering ram on the front arrived at the scene.
Traffic was rerouted through the town of about 2,000 residents in eastern Washington County.
One of the negotiators inside the building was Deputy Mel Swope, Deborah Trumpower's brother.
In addition to Swope and Blair, other deputies inside the building were Robert Whittington and Richard Schleigh. A state police trooper also was inside.
Robert Hurst, a Hadley Farms employee, said he was reporting for work Tuesday morning when he heard someone yelling.
"They were yelling for everyone to get out," Hurst said. "So I got out."
He and other workers gathered outside the plant Tuesday morning, waiting to see what would happen.
Before Trumpower's surrender some of the neighbors were told to leave their homes and the Smithsburg Market, adjacent to Hadley Farms, was closed.
Beatrice and Claude King, who live two houses away from the bakery, were awakened after 4 a.m. when their dog started barking and they saw lights flashing.
"It's funny how people always snap around the holidays," she said. "I was holding my fingers crossed that nobody would get hurt."
Jason Sturn, general manager of Hadley Farms, said the company has two shifts, employs 120 people and supplies breakfast items to Disney World, airlines and the Marriott Corp.
Kent Reynolds, the owner of the Smithsburg Market, said the hostage situation hurt business on one of the busiest days of the year. A lot of people had placed special orders for Christmas, he said.
"We'll work through the night and have orders ready tomorrow," he said.
Staff Writer Laura Ernde contributed to this story.