(CBS) — A desperate search continues for a Chicago man, and now there is a $10,000 reward.

His name is John Cunningham, and he was last seen near a forest preserve in southwest suburban Palos Park.

He was Christina and John Cunningham Sr.’s only child. He has been missing for a week now.

His parents say the 27-year-old was visiting their Palos Park home last Thursday. He was on the phone with his boss, quitting his job with a securities firm. Something upset him so much he walked off with just the T-shirt and sweatpants he was wearing.

“I started driving to find him. He was already off our street. I didn’t know where he went,” Christina Cunningham tells CBS 2’s Pamela Jones.

She says he’d walked about a mile to Cherrywood Drive when she caught up with him. But her son waved her away and ignored her attempts to get him to talk. He vanished soon after.

The junior Cunningham, who graduated from law school, is known as the life of the party and a loving friend. His dad wonders whether the burden of wanting to right the world’s wrongs just became too heavy.

“I think it took a toll on him a little bit,” John Cunningham Sr. says.

The Cook County Sheriff’s Department and more than 200 volunteers combed the forest preserve’s surrounding subdivisions.

Authorities say it would take new information to bring searchers back out to look for the missing man. They say it’s too early to speculate what may have happened to him.

The family has hired a private investigator to help police with the search. For more information, click here.