HOLBROOK, N.Y. (CBSNewYork) — Two men were found dead of apparent carbon monoxide poisoning in a Long Island auto shop, police said.

Officers found the bodies of the shop’s owner, Porfiro Alvarez, 54, of Freeport, and his employee, Jose Rufino Gonzalez, 25, of Bellport, inside Super Auto Detail at 1372 Lincoln Avenue in Holbrook around 6:15 p.m. Thursday.

READ MORE: First Responders Pay Tribute To Sean Patrick Carroll, Volunteer Firefighter Killed In Thanksgiving Day House Fire

Alvarez’s family became concerned after they were unable to get in touch with him since Tuesday and called police when they were unable to get into the locked auto shop Thursday.

When officers made their way into the shop, they found Alvarez next to his 1989 GMC van and Gonzalez on a mattress in the back of the vehicle, authorities said.

Both men were pronounced dead at the scene.

READ MORE: Attorney General's Office Releases Another Round Of Transcripts In Andrew Cuomo Investigation

“It wasn’t uncommon that we didn’t hear from him for days at a time because he would sleep here,” the victim’s son, Eduardo Alvarez, told 1010 WINS’ Mona Rivera. “My uncles came down and unfortunately it was already too late.”

The van had apparently been left running. Police said the vehicle’s ignition was on, the heat was set on high and it appears that it had run out of gas.

It appears Alvarez and Gonzalez were apparently overcome by the carbon monoxide fumes from the van, police said.

Ryan Curran, whose auto body shop shares a wall with Super Auto Detail, said he went home sick on Wednesday.

“My head just started hurting and I was like throwing up like yellow stuff,” Curran told Rivera. “Then last night, cops called my dad to the shop and that’s when they figured out it was carbon monoxide.”

MORE NEWS: Families Of Stolen French Bulldogs Relieved To Have Pets Back, But Warn Other Long Island Dog Owners To Be Careful

Curran said the victims’ shop had no heat and they were probably running the vehicle to stay warm, Rivera reported.