Highland Park, IL- A north suburban couple was found dead of carbon monoxide poisoning by their son, a firefighter, on Monday morning.

The Highland Park Fire Dept. lieutenant went to visit his parents at their home in the 1200 block of Golf Avenue about 8 a.m. Monday and found his father unresponsive on the main floor, according to Highland Park police.

He immediately began CPR and called 911 for an ambulance, police said. His mother was found unresponsive in an upstairs bedroom.

Both Pasquale, 79, and Rina Fontanini, 76, were pronounced dead at the scene, police said.

It appears the elder Fontanini heard the alarm on the carbon monoxide detector, and found that the family car, which has a keyless ignition, was running in the attached garage, police said.

He opened the overheard garage door to alleviate the fumes,but“tragically it was too late as the high levels of carbon monoxide were affecting him,” a statement from police said.

An investigation found extremely high levels of carbon monoxide throughout the home, police said.