KINGMAN — An autopsy performed on a Kingman woman who died Valentine’s Day determined her death was caused by carbon monoxide poisoning.

Sharmallee Ann Johnson, 21, was found dead Saturday in the bathtub of a Kingman motel. Her boyfriend, 23-year-old Fredrick Louis Herzer was found unconscious on a couch in the living room, Kingman Police Lt. Dean Brice said.

The Kingman couple had checked into the motel’s suite in the 2300 block of Andy Devine Avenue Friday for Valentine’s Day.

Herzer was taken to Kingman Regional Medical Center, then flown to Barrow Neurological Institute in Phoenix in critical condition.

Herzer is still being treated at the hospital but has been released from the intensive care unit, Brice said.

The carbon monoxide poisoning is believed to have been caused by a leak from an exhaust system in the boiler room below the room the couple was staying in at the motel.

A neighboring room also had to be evacuated but no other injuries were reported.