We now know how the alarm was sounded when someone at Artem Chigvintsev's home called 911.
Sources connected to the investigation tell TMZ ... a call came in around 8:30 AM, reporting a "medical emergency" at the home. It's unclear who made the call.
As paramedics and the fire department were en route, someone from the house called 911 again to cancel the request. They did not say why, but we're told paramedics and fire returned to their stations .