Lowenthal tweeted about the news Thursday.
The man who entered Lowenthal's office told those inside it was "immoral" and "disgusting" to hang a pride flag next to the Americal flag.
"The fact that someone would grab a flag that they didn't like and not just throw it on the ground, but stomp all over it ... it's certainly shocking," Lowenthal, a Democrat from Southern California, told the Times.
Lowenthal was not at his office during the incident, but his staff called police, who spoke with the man. "They told us he didn't break any rules or any laws, so they let him go," the congressman said.
Lowenthal told the Times he has displayed the Pride flag outside his office since 2013, the year he came to Congress. He serves as the vice chairman of the House LGBT Caucus. He said he mostly gets compliments about the flag, with people saying they're happy he has it up. This was the first negative reaction he's ever received regarding the flag, he said.
"I just think it's terrible. I'm just shocked that it happened," Lowenthal told the Times. "It just reinforces my belief that more work needs to be done."
"We're proud to fly the Pride flag, and we're going to continue to show how proud we are," said Lowenthal, who put the flag back up after the incident.
