A tense standoff between police and a gunman who had stormed into a veterans home in California and taken three employees hostage came to a grim end Friday night when officers entered the room the gunman was in to find him and all three hostages dead.

The man had shown up at the largest veterans home in the United States with a rifle in the morning and exchanged gunfire with a sheriff's deputy before crashing a farewell party for employees of a organization that works with recent veterans and taking a number of hostages.

The confrontation stretched throughout the day and into the night; officials said that a number of hostages had been released early on, but three employees remained in a room with the gunman and teams of federal, state and local law enforcement officials and hostage negotiators from three agencies had been unable to make contact with the gunman or the hostages.

But around 6 p.m. local time, officers entered the room and discovered the bodies of the four people, officials said at a briefing Friday night.

The standoff had lasted more than eight hours at the complex, the Veterans Home of California-Yountville, as teams of heavily armed law enforcement officers from state and federal agencies swarmed around the building with worried family members waiting outside. It was not immediately clear when the hostages were shot.

Police said the gunman had been holed up in a room with three hostages, all employees of Pathway Home, a nonprofit on site that works to reintegrate recent veterans back into civilian life, including those suffering from post-traumatic stress disorder. Other hostages had been released earlier in the day.

The incident unfolded around 10:20 a.m., when the gunman showed up and exchanged fire with a sheriff's deputy who had arrived to respond to an emergency call, highway patrol officials said.

At some point, the gunman appeared at the goodbye party for one of the employees of Pathway Home, according to Larry Kamer, a former member of the nonprofit's board of directors.

"There was a going-away party for a couple of the staff who were leaving today. Today was their last day. They were having cake and toasting and apparently he just walked in with this rifle," said Kamer, who told reporters that his wife, a Pathway Home employee, was at the event.

Kamer said his wife was one of those allowed to leave.

Officials said that they had not received any reports of injuries to any civilians or officers, but they did not know the status of the three hostages. They declined to publicly identify the gunman but said they were trying to reach him on his cellphone.

State Sen. Bill Dodd, who represents the area, said on NBC one of the hostages was a mental health professional from the clinic. The gunman had been dismissed from a veteran's program at the facility this week, Dodd said.

SWAT teams on scene of #Yountville veterans home shooting. LIVE VIDEO: https://t.co/0qyCtycosx pic.twitter.com/xOp5G2BQSW

— NBC Bay Area (@nbcbayarea) March 9, 2018
The scene brought fear and terror to the small town of about 3,000 in the heart of California's wine country as heavily armed officers and armored vehicles descended on an area perhaps most famous for the upscale restaurant the French Laundry. The winery Domain Chandon is less than a half mile away from the veterans home.

The complex was shut down after the shooting, with those inside being asked to shelter in place. Some 80 high school students visiting a theater on the property were put in a "lockdown situation" before being evacuated, Napa County Sheriff John R. Robertson told reporters. Nearby facilities, including a golf course, were also evacuated.

Larry Gomez told the television station ABC 7 he was hustled off the course by officials in golf carts.

"They said shots were fired, and the golf course was being evacuated," Gomez said. "Nothing surprises me in this day and age anymore."

Law enforcement agents from the Bureau of Alcohol, Tobacco, Firearms and Explosives and the FBI assisted in the response, joining deputies from the Napa County Sheriff's Office as well as a SWAT team from the highway patrol. Hostage negotiators from at least three agencies were on the scene.

Concerned family members gathered outside, some still waiting to make contact with their loved ones.

"There's just no answer and the anxiety just continues," one man, who said his father lived at the home, told NBC.

Photographs from local media outlets showed armored vehicles and officers in tactical gear at work outside the building. The sheriff's office asked people to avoid the area and said there was no public safety threat beyond the area where the gunman was contained.

June Iljana, a spokeswoman for the California Department of Veterans Affairs, said staff at the home were cooperating with law enforcement officials.

"The safety of our residents, workers and the community is our top priority," she said in a statement.

The Yountville residence, home to 1,000 elderly or disabled veterans of wars dating back to World War II, is the largest home for veterans in the country, according to the Department of Veterans Affairs.