When Rinaldo returned from Saint Padre Pio, in Kleinburg, Mark was still not home.

The distressed parents headed out to search for him, Rinaldo on the bike and Maria in her car.

Despite looking far and wide, they found nothing.

Since then, they have been relying on police to scour the William T. Foster Woods nearby their home, located off Islington Avenue, just south of Major Mackenzie.

Police are also using a helicopter to search and an aerial police drone with an infrared search camera.

This is not the first time Mark has left the home and not returned, but the last time, about three years ago, the family received a collect phone call from him after he had fallen asleep at a Woodbridge bakery.

But now, the family is concerned the heat may have caused him to fall asleep and then awoken, dehydrated and disorientated.

Mark suffers from a "major depressive order”, according to Maria, who explained he's only been taking his medication sporadically over the past few months.

"He had a major setback recently when he fell off his bike in a local park — it traumatized him I think. He had been doing so well," she said, adding Mark also suffers from social anxiety and is unlikely to talk to strangers. "We don't know anything, where he went, in which direction. We just hope that someone will have seen him so we can start to look there. We're asking the public to check parks and woods. We’re concerned he might be isolated."

Mark is described as white, five-feet, eight-inches tall, 140 pound, with a thin build, short dark brown hair and brown eyes.

He walks with his arm tucked close to his body because of the bike injury and his wallet and phone were left at his home.

He was last seen wearing a long-sleeved burnt orange and grey Reebok shirt with stitching in the front along with black sweatpants and brown shoes.

Anyone with information is asked to call police at 1-866-876-5423.