Mexican officials have charged an American man for allegedly lying about the slaying of a Canadian man in a beach resort city.

State police commander Omar Barajas said late Monday that investigators believe Michael Thompson of Chicago knows who killed Bouabal Bounthavorn, 29, of Burnaby, B.C.

Bounthavorn was shot in the head after opening the door of his room at the Hotel Riu in the Baja California peninsula city of Cabo San Lucas, police say. His girlfriend was shot in the ankle.

Thompson, who has been held as a witness since the killing, initially told police he saw someone argue with and then shoot Bounthavorn at the hotel on May 15.

He has now been charged with giving a false statement to investigators.

Police said they have detained a Mexican man in connection with the case, but wouldn't give any further details.