The search for a former U.S. soldier suspected of killing four people at a bar in Montana stretched into a fourth day Monday, with deputies scouring the mountainous terrain by foot and air after the man escaped in a stolen vehicle containing camping gear.

Authorities say Michael Paul Brown, 45, fatally shot four people Friday morning at The Owl Bar in the small town of Anaconda with a rifle that police believe was his personal weapon. He fled in a white pickup that he later ditched and stole another white vehicle stocked with clothes, shoes and other supplies.

A female bartender and three male patrons were killed. The shooting rattled the tight-knit town of about 9,000 people, and many residents remain on high alert with the suspect still at large.

Here’s what is known about the search.

How is the search progressing?

Law enforcement officers from across the state have been brought in to assist with the search for Brown, Montana Attorney General Austin Knudsen said. Search teams include multiple local, state, and federal agencies and are surveying the area both on the ground and by air. Helicopters whirred overhead as Anaconda residents adjusted to daily life after the shooting.

The effort initially concentrated on an area off Stumptown Road, west of Anaconda. By Saturday, they had expanded the search to the Barker Lakes area and had more than 250 people out searching, plus canine detection units and drones using heat-detection technology, authorities said.

Knudsen said investigators are now searching all possible options for Brown’s whereabouts, including the woods where he hunted and camped in his youth. About 22 square miles (57 square kilometers) of forest southwest of Anaconda have been closed to the public by the National Forest System as the manhunt carries on, District Ranger Cameron Rasor said Monday.

Business owners locked their doors Friday and sheltered inside with customers. A lockdown of the Stumptown Road area was lifted on Saturday, but many local businesses were slow to reopen.

On Monday, the U.S. Marshals Service announced a reward of up to $10,000 for any information leading to Brown’s capture. They said he is believed to be armed and dangerous.

Who were the victims?

The victims were identified on Sunday as bartender Nancy Lauretta Kelley, 64, and patrons Daniel Edwin Baillie, 59, David Allen Leach, 70, and Tony Wayne Palm, 74.

All four were residents of Anaconda, which is situated between rugged mountains about 25 miles (40 kilometers) northwest of Butte.

Robert Wyatt, 70, told The Associated Press he was neighbors with Leach at a public housing complex for elderly people and people with disabilities. Leach was deaf and kept mostly to himself, Wyatt said, but he was always happy to help his neighbors.

Kelley’s daughter, Kristian Kelley, told NBC News her mother was a recently retired oncology nurse who picked up the bartending job to fill some of her free time. The daughter said she was shocked to hear about the shooting in a text message from a friend and grew worried when her mother didn’t answer the phone. Upon driving into town, she learned her mother was among the victims.

In a town where “everybody knows everybody,” the entire community is hurting, said resident David Jabarek, 70.

What is known about the suspect?

Brown served in the Army as an armor crewman from 2001 to 2005 and deployed to Iraq from early 2004 until March 2005, said Lt. Col. Ruth Castro, an Army spokesperson. Brown was in the Montana National Guard from 2006 to March 2009 and left military service at the rank of sergeant, Castro said.

Brown lived next door to The Owl Bar, according to owner David Gwerder, who was not present during the shooting Friday morning. It was widely believed that Brown knew at least some of the victims.

In a photo released by law enforcement, Brown appears gaunt, barefoot and wearing nothing but black boxer briefs.

Brown’s niece, Clare Boyle, told The AP that her uncle has struggled with mental illness for years, and she and other family members repeatedly sought help for him. She described him as “a sick man who doesn’t know who he is sometimes and frequently doesn’t know where or when he is either.”