Renton, WA – Renton firefighters and police officers believe two men died of carbon monoxide poisoning after they were discovered dead inside a home Monday.

Renton police say relatives visited the home about 3 p.m. in the 500 block of Seneca Avenue Northwest to find the 66-year-old resident and a 28-year-old visiting friend dead.

The 66-year-old man’s dog had also died.

The fire department determined the home contained an elevated level of carbon monoxide in the home.

The investigation indicates that the resident left his car running in the garage with the garage door down to charge the battery, according to the Renton Police Department.

The car was rarely used and the victim reportedly routinely charged the battery by running the car with the garage door closed.

Fire and police personnel found the victim’s car in the garage with the key in the “on” position, but the car was no longer running and the battery was dead. Investigators believe the car ran out of gas.

The Medical Examiner is looking into the cause and time of death.