Police say Van Bui used his job at the popular Honey Badger Caf? in Alhambra to lure his victims. They say he befriended at least two young women and kept in contact with them via social media.
Police say he would then arrange to meet up with them or invite them to his residence in a gated Monterey Park community, where it's possible he drugged them before sexually assaulting them.
"This is typical of sexual predators: They use social media so they can hide their identity, their intent, and perpetrate their crime," said Monterey Park Police Lt. Bill Cuevas.
Jerry Tou, the manager of Honey Badger Caf?, said everyone there is horrified by the allegations.
"The environment we provided to have a cozy environment for our customers, he found a very sleazy way to take advantage of that, and it upsets us a ton," said Tou.
Young women who frequent the neighborhood were equally shocked.
Tou says Van Bui never showed any signs of alarming behavior. His coworkers even say he was working there to make money to take care of his grandparents.
"He was extremely nice to the staff. He was extremely hardworking," said Tou.
Van Bui has been charged with five counts of sexual assault and was held on $1.5 million bail.
"We seized the phone, some evidence that was located at the suspect's residence, and we do believe that there are additional victims," said Lt. Cuevas.
Investigators say they are waiting for lab results before they can confirm whether the alleged victims were drugged.
Anyone with information related to the case is urged to call the Monterey Park Police Department at (626) 307-1236.