A New Jersey man charged in the fatal stabbing of a 16-year-old girl was reportedly in the U.S. illegally at the time of the alleged crime.

Bryan Cordero-Castro, 20, was charged with murder, weapons possession and attempted escape in connection with the stabbing death of Madison Wells. Cordero-Castro is a Guatemalan native who was living in the U.S. illegally after overstaying his visa, according to the Asbury Park Press.

Friends told WABC that Cordero-Castro and Wells had been dating for about a year before the teen’s death.

One friend described the pair to the Asbury Park Press as being “inseparable.”

“They used to hang out every day,” Hafett Barrates, 18, told the newspaper. Barrates added he didn’t know what could have led to the stabbing.

Wells, a Long Branch native, had lived for a time in Florida before moving back to New Jersey in 2014. She was just starting her junior year at Long Branch High School at the time of her death.

Wells was wounded but alive when she was found by Long Branch police officers responding to a report of a stabbing Saturday night. She was taken to Monmouth Medical Center, where she died about an hour later, police said.