"Joseph died trying to protect others," Sheriff Doug Gillespie said.
By now, police had arrived, and two five-officer teams entered the massive store. Near the back, one team confronted the Millers, and exchanged fire. At one point, Jerad Miller tried to blast a rear emergency exit door open with a shotgun, but police had blocked it with a car and he could not escape.
One officer went with store security to screens showing feeds from surveillance cameras and saw that Jerad Miller had built a makeshift barricade around his wife.
As police closed in, Amanda Miller shot her husband several times with a handgun, killing him. She then shot herself in the head. When officers arrived, she was still breathing, and was taken to the hospital. She later died.
Police found hundreds more rounds of unspent ammunition in the Millers' bags.
The couple moved to the Las Vegas area in January, police said. Amanda Miller had worked at a Hobby Lobby craft store there until she was fired in April, the chain store said in a written statement.
Jerad Miller, 31, was convicted of felony vehicle theft in Washington state, and several other offenses, including phone harassment, driving under the influence, theft and malicious mischief, between 2001 and 2003, according to a Washington State Patrol database.
He also had a criminal record in Indiana.
Miller attended Kennewick High School in Washington state for one semester in 1999, his freshman year, district spokeswoman Robyn Chastain said. The district had no other record of him attending schools in the district, or of what he did when he left the school.
He and his 22-year-old wife were married in August 2012, according to a marriage license on file in Indiana.
When police descended on their apartment complex Sunday night in a rundown neighborhood, officers evacuated other residents.
On Monday, Sheriff Gillespie said he was pairing officers together for safety and that, for now, 300 will be on patrol — twice what is normal.
Asked about worries that more officers may be targeted, he responded: "Is that weighing? Sure, there's no doubt about it."
Ammon Bundy said supporters of his father are saddened by the killings and "have had no quarrel" with Las Vegas police.
"The only thing worse than (government) tyranny is anarchy," he said. "And we certainly recognize that."
Pritchard reported from Los Angeles. Associated Press writer Eugene Johnson in Seattle and researcher Judith Ausuebel in New York contributed to this report.