A New York family is desperate for help after the disappearance of 21-year-old Miles Applebaum this week.

"Our horrible fear is that we'll never find him again," his father, Edward Applebaum, told The Huffington Post. "It's our worst nightmare."

Miles Applebaum hasn’t been seen or heard from since Monday morning, when he left his home in Armonk, a hamlet in the town of North Castle about 50 miles northeast of New York City.

"He said, 'Goodbye, I'm going to work, I love you,'" Edward Applebaum said of his last interaction with his son.

Miles Applebaum is a junior on medical leave from Temple University in Philadelphia. He works for a local music school and volunteers at a nature center, his father said.

"When he never came home for dinner Monday night, we called the police," said Edward Applebaum.

The distraught father said he and his wife are very concerned for their son, the middle of their three children, because he has been suffering from severe depression in recent months.

"He was suicidal and has been on and off various medications," Edward Applebaum said.

There has been no activity in Miles Applebaum's bank account and his phone has not been turned on since Monday morning -- something his dad said is "out of character."

His vehicle, a 1999 forest green Volvo S80 with New York license #Z524CL, also is missing.

The North Castle Police Department is investigating Applebaum's disappearance.

Edward Applebaum said investigators are conducting a forensic examination of his son's computer, hoping to find clues about his disappearance.

"I'm hopeful," Edward Applebaum said. "It's just that as the hours tick by, my optimism is waning."

Anyone with information is asked to contact North Castle police at 914-273-9500.