A convicted sex offender allegedly cut off his GPS ankle bracelet just before attempting to kidnap a woman at gunpoint in a coffee shop parking lot Thursday, police said.

The victim, an Alhambra woman in her 20s, escaped with the help of a good Samaritan who interrupted the 9:30 a.m. attempted abduction outside Starbucks, 1131 S. Fremont Avenue, Alhambra police Sgt. Edward Rodriguez said.

Frank Hernandez, 64, of Rosemead was arrested about an hour later on suspicion of attempted kidnapping, police said.

According to the California Department of Justice sex offender registry, Hernandez was released from prison in 2011 after serving a sentence for kidnapping with intent to commit a sex offense, rape by force or fear, rape by force and oral copulation.

“Mr. Hernandez is required to wear an ankle bracelet as part of his conditions of parole,” Sgt. Jerry Johnson said in a written statement. “However, evidence showed that he cut the ankle bracelet off shortly before committing the crime.”

The victim went to the Starbucks to meet with Hernandez, whom she was acquainted with through church, Rodriguez said.

“When she arrived, (Hernandez) approached her before she could exit her car,” Johnson said. “The victim said he pulled a handgun and threatened to kill her if she did not let him in her car.”

The frightened woman called out for help, catching the attention of another woman who was passing by, officials said.

“This witness approached (Hernandez) and told him to leave the woman alone. The suspect then fled to his nearby car and drove away,” Johnson said.

But the quick-thinking good Samaritan “was astute enough to take a picture of the suspect’s car,” Alhambra police Detective Sgt. Joe Flannagan said. The photo included the car’s license plate.

It was unclear if the woman who intervened was aware the suspect was armed.

In addition the good Samaritan, Flannagan also credited the victim for creating attention to aid in her own escape.

“That was very brave on the part of the victim,” he said.

Los Angeles County Superior Court electronic records regarding Hernandez previous case were incomplete, however they indicated he was ordered to stand trial on charges of rape and kidnapping in Alhambra Superior Court in August 1990.

Hernandez’s profile in the DOJ registry indicates he uses numerous aliases, including: Edward Davilla, Robert Diaz, Manuel Frank Flores, Manuel Hernandez, Gary Sole Lopez, Gary Lopez Sole, Carlos Ruiz Martinez and Carlos Martinez Ruiz.

According to county booking records, Hernandez was being held without bail pending his initial court appearance Monday in Alhambra Superior Court.