The crime occurred about 9:50 p.m. Thursday in the 9200 block of Steele Street, said Detective Sgt. Richard Lewis of the Los Angeles County Sheriff's Department.
"The individual was followed home, we're not sure from where, and was contacted by three individuals who stole cash and the 3-month-old French bulldog," Lewis said.
One of the three male suspects was armed with a handgun, Lewis said. No injuries were reported.
According to the preliminary investigation, an unspecified amount of cash was taken, along with a rifle and at least one cellphone.
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No description was available of the suspects or of any vehicle they may have used, Lewis said.
News of the incident rattled the nerves of some nearby residents.
"I'm going to lock my doors more, I'll tell you that," Carolyn Warner, who lives in the neighborhood, told ABC7. "This is scary. I'm one that I don't think anything's ever going to happen, but it's obvious (that) it can."
Detectives were working to find any surveillance video, including ring camera footage, that might help in the investigation. Anyone with information on the case was urged to call Lewis at the sheriff's Temple Station, (626) 285-7171.
City News Service contributed to this report.