On Friday, Sonia Ulrich posted that she and two female friends had been enjoying the happy hour at Fig, a restaurant inside the Fairmont Hotel off of Ocean Avenue, when they saw a man put something in another woman's drink.
The trio thought the woman had been on a date with the man; she had gone to the bathroom when he allegedly slipped something into the drink, according to Ulrich.
The woman was stunned, telling Ulrich that the two worked together and had known each other for more than a year, according to Ulrich's post. He was actually one of her best friends, she said.
Meanwhile, the woman who first noticed the incident -- identified in the post as Marla Saltzer -- flagged down a waiter and explained to him and her friends what she saw.
The man apparently then realized he was being watched by another woman, Monica Kenyon, who was also with the group, Ulrich wrote.
Meanwhile, the would-be-victim sat down at her table after the restroom encounter with Ulrich.
After learning of the alleged attempted drugging, the restaurant's manager went over to the pair to ensure everything was OK, and to offer the woman water.
She then continued the dinner with the man until Santa Monica police showed up to question him, according to the post. He was taken away.
Later, the head of the security went to the women's table to tell them that because of their quick-thinking actions, they were able to review security footage and found that a camera had captured the incident.
"They got him on tape. They had proof of him drugging this girl. They took the glass away as evidence," Ulrich wrote.
Police confirmed they have the surveillance and the drink in their possession.
As word of what transpired spread through the restaurant, other diners walked over to the women and thanked them for taking action, she said. A number of people told them they or someone they knew had been the victim of a drugging.
Hsu, 24, was arrested Thursday on the felony charges, according to Los Angeles County jail records. His total bail amount was set 1 million, the record showed.
The case was expected to be presented to the L.A. County District Attorney's Office on Tuesday, according to police.