WASHINGTON — President Biden on Thursday honored 18 people killed in two California mass shootings, saying “we have to be there” with the communities that have been forever scarred by gun violence.

“Our prayers are with the people of Monterey Park and Half Moon Bay, and after yet another spree of gun violence in America,” he said at a Lunar New Year reception at the White House.

Eleven people were killed at a Southern California ballroom dance hall late Saturday and seven others died Monday at two mushroom farms in the northern part of the state.

Biden said he had spoken with Brandon Tsay, 26, who was at a second dance hall a few miles from the scene of the tragedy in Monterey Park when the same gunman entered, brandishing his weapon. Tsay disarmed the gunman, who then fled.

He praised Tsay’s courage, calling him a “genuine hero.”

“Brandon said he thought he was going to die, but then he thought about the people inside,” Biden said, asking the largely Asian American audience to ponder what could have happened had Tsay fled himself.

“I think sometimes we underestimate incredible acts of courage,” the president said. “Someone has a semiautomatic pistol aimed at you and you think about others. That’s pretty profound, pretty profound.”

The shootings were carried out during celebrations of the arrival of the Lunar New Year, one of the most important Asian holidays, and sent fear through Asian American communities already dealing with increased violence directed at them, some of it due to misinformation about the coronavirus.

Authorities said Huu Can Tran opened fire late Saturday on a mostly elderly crowd of dancers at the Star Ballroom Dance Studio in Monterey Park. Nine people also were wounded. Tran, 72, was later found dead from a self-inflicted gunshot wound.

Days later, farmworker Chunli Zhao, 66, opened fire at two mushroom farms in Half Moon Bay on Monday, killing seven current and former co-workers, police said.

The White House had scheduled its Lunar New Year celebration before the shootings.

Both communities “will be affected by what they saw and what they lost for the rest of their lives,” Biden said, referring to the trauma inflicted and the need for treatment. “And as a nation, we have to be there with them. We have to be there with them. We don’t have a choice.”

He led the gathering in a moment of silence in honor of the victims.

Biden had ordered American flags on federal facilities lowered to half-staff through sunset Thursday out of respect for the Monterey Park victims. He said Thursday that he has been in touch with California Gov. Gavin Newsom. He also sent Vice President Kamala Harris, a native of the state, to Monterey Park on Wednesday to offer condolences on behalf of the government.

Biden had been in California on Jan. 19, just two days before the dance studio shooting, to survey flood damage along the state’s central coast following days of heavy rains. He spoke with Tsay earlier this week.

“Thank you for taking such incredible action in the face of danger,” Biden told Tsay in a brief video of the conversation that the White House shared Thursday on Twitter. “I don’t think you understand how much you’ve done for so many people who are never even going to know you.”

Tsay replied that he was still processing what had happened.

“For you to call, that’s just so comforting to me,” Tsay told the president.