The holiday season has turned into a nightmare for the family of a Pennsylvania nurse who disappeared under mysterious circumstances last week.

"It's the hardest thing we've ever had to deal with," Jack Kochu, the nurse's father, told The Huffington Post. "All we have is questions and despair. If we could just know something -- it may not be the answer that we want -- we would have an answer. Right now we don't have anything."

Jack Kochu's son, 22-year-old Paul Kochu, was last seen at his Pittsburgh apartment around 1 a.m. on Dec. 16. According to the elder Kochu, Paul's roommates were the last people to have contact with him.

"Paul and his two roommates had gone to a local bar to watch a football game," said the distraught father. "[Paul] left around midnight and his roommates stayed behind. About 30 minutes later, they got a phone call from [Paul] that he had cut his hand while trying to pick up a broken glass."

Paul Kochu's roommates left Smoking Joe's, the South Side Pittsburgh bar where they had been hanging out, to help him mend his wounded hand. Jack Kochu said his son's injury was described to him as a "small cut" that did not "appear bad enough to require him to go to hospital for stitches."

After helping Paul Kochu attend to his injury, his two roommates left to pick up food for the three of them. Upon their return, he was gone. There was no heads-up given and no note; he had simply vanished.

"His wallet, his car keys and his cellphone were not there. However, his car was still in the same spot he had parked it in the night before," said Jack Kochu. "We're baffled."

According to his father, Paul Kochu is a 2010 graduate of Owen J. Roberts High School in Pottstown, which is located approximately 275 miles southeast of Pittsburgh. In high school, he was active in baseball and football.

The young man recently graduated from the nursing program at Duquesne University and works in the Intensive Care Unit at Allegheny General Hospital, where he failed to show up for his scheduled 7 a.m. shift on Dec. 18.

Jack Kochu said his son is very responsible, has never missed classes or work and would not take off without notifying someone.

"It is 199 percent uncharacteristic of Paul not to be where he was supposed to be," he said. "He's wanted to be a nurse the last six years. There is absolutely, positively, no way he would miss work."

Calls for comment from HuffPost to Pittsburgh police were not immediately returned Monday. According to Jack Kochu, authorities are working hard to locate his son.

"The detectives are working very hard," he said. "They've interviewed the roommates, scoured the house they live in and the river banks in Pittsburgh. We also had a search party of upwards of 80 people here on Saturday. Right now there are no theories and the investigation is ongoing."

Paul Kochu is described as 6 feet, 1 inch tall, and 180 pounds with brown hair and blue eyes. A reward of $15,000 is being offered for anyone with information leading to his whereabouts, according to his father.

"All we want is Paul," said Jack Kochu. "I'm not going to come after anybody for any type of retribution. We just want Paul. That's all, and it just takes one person to help us."