A man allegedly kidnapped a teenage girl in San Diego on Sunday (local time) after she and a group of teenagers tried to expose the man as a paedophile, police said.
The San Diego Sheriff's Department said the girl was taken after she and a group of teenagers used a social media app to contact 32-year-old Robert Dreyfus, who was allegedly looking for under-aged girls to have sex with.
Dreyfus agreed to meet the group, police say, and convinced a 17-year-old to get in his vehicle. He immediately drove away.
"The victim was able to send a message for help to the group, who called law enforcement," a police statement said.
Dreyfus was later arrested and charged with kidnapping as well as a raft of other offences.
Authorities strongly discouraged the public from taking potential criminal matters into their own hands, the sheriff's department said.
"These types of situations can be extremely dangerous and should be handled by your local law enforcement agency."