CHICAGO (CBS) — One man was killed and another was critically injured early Thursday in a fire at a mobile home park in southwest suburban Oak Lawn.

Neighbors said they could only watch as the fire burned through two mobile homes at the Airway Manufactured Housing Community at 90th and Cicero.

Oak Lawn firefighters arrived at the trailer park around 1:45 a.m., and flames already were raging in two mobile homes, according to Fire Chief George Sheets.

Firefighters found one man outside one of the mobile homes. Neighbors said he had emerged in flames, but at first they could not see him due to the heavy smoke.

Neighbors said two police officers stood by just watching as the man screamed for help.

“It was just something I’ll never forget, him screaming ‘Help!’” Tryston Radtke said. “He just kept saying ‘Help!’ He was like, ‘I’m right here!’”

The man was taken to Advocate Christ Medical Center in critical condition.

Another man was found dead inside the other trailer.

Sheets said it was the third time someone has died in a fire at the mobile home park in the last three months.

Police said they are investigating the possibility the fire was the result of arson.

“Information that we talked to with witnesses and other residents of the trailer court indicated that we should activate the major crimes task force, and we are looking at that as a possibility, yes,” Oak Lawn Police Chief Michael Murray said. “We are looking at it as a possible intentional act.”

The cause of the fire was under investigation.