PARIS — In a series of videos on the live-streaming app Periscope, she said that her name was Océane, that she was 19 and that she worked in a retirement home. Seated on a couch, she smoked cigarettes, played with her cat, and showed off her tattoos: a rose on her left forearm, a small heart on her right thumb. She engaged with Periscope followers, who asked about her life and her hobbies.

At 4:29 p.m. on Tuesday, while recording herself on Periscope, the woman threw herself under a train at the Égly station, about 25 miles south of Paris, on the C line of the regional train system known as the R.E.R.

On Wednesday, French officials said they had opened an investigation into her death.

Éric Lallement, the local prosecutor, said the young woman, whom he did not identify, had sent a text message to a friend of her former boyfriend, saying the ex-boyfriend had abused and raped her. In the text message, “she declares she is ending her life because of the evil that he did to her,” Mr. Lallement said in a statement.

He added that investigators were examining the woman’s mobile phone and were working to obtain the original videos from Periscope. The investigators, he said, had talked to the woman’s relatives, and they had described her as being psychologically fragile and as having had a troubled relationship with the ex-boyfriend.