UNION CITY -- Joshua Gonzalez-Perez lived for the outdoors, whether it was hiking, taking long bike rides on dirt trails or trying to catch a fish. On Saturday, he called his aunt to discuss a planned excursion and to arrange transportation home.

But Irma Jacques never received the call to come get her nephew. On Monday, she was in mourning after Gonzalez-Perez, 21, was found unconscious in a trash can outside a friend's Union City home. He later was pronounced dead.

"We just want to find out what happened," Jacques said of the chilling discovery Sunday in the 33900 block of 10th Street, on the southern edge of Union City's Decoto district. "He's a human being, and he didn't deserve to be stuffed in a garbage can. No human deserves to be treated that way."

A resident at the home, Andrea Hernandez, said her 66-year-old mother discovered Gonzalez-Perez in the can about 6:30 a.m. Sunday when she went outside to take out some trash. The man was feet first, as if he was crouching down in the large green can, she said. No blood or debris surrounded the city-issued bin.

"She was yelling and said, '(Andrea), Josh is in the trash can,'" Hernandez said. A younger male relative came outside and started shaking the can and yelling at Gonzalez-Perez to wake up. The family called 911 when they realized he was unconscious.

Rescuers took Gonzalez-Perez to a hospital, where he was pronounced dead from undisclosed injuries, police said.

"I'm still kind of shocked," Hernandez said. "We've known him and his family forever."

There were no obvious signs of trauma on the body or foul play, Cmdr. Ben Horner said. Gonzalez-Perez had alcohol in his system when he was discovered, according to media reports.

"There are a number of theories. He could have been placed in there by friends as a prank," Horner said. "And it was cold that night. The key piece of the puzzle will be the coroner's report."

The autopsy, which will likely be conducted Tuesday, may show whether exposure played a role in the man's death, Horner said. Temperatures Sunday morning hit a low of 39 degrees in the area, the National Weather Service said.

The trash bin holding Gonzalez-Perez did not belong to the home where he was found, Horner said, and was likely wheeled there from another residence. It is unclear if the trash can belonged to another nearby home.

The woman who discovered the body was one of many friends Gonzalez-Perez stayed with in the area, Horner said. Gonzalez-Perez was staying at another 10th Street home at the time his body was found and also has listed residences in Hayward.

Family and friends of Gonzalez-Perez, including the ones who were hosting him, are being cooperative with the investigation, Horner said.

Gonzalez-Perez recently graduated from Job Corps, where he received his certification in computer technology, Jacques said. He grew up near Lodi and battled a genetic medical condition that caused him to have bone pain for most of his life, Jacques said.

"He was just a happy person," Jacques said, fighting back tears. "He suffered and had a lot of pain, but he dealt with it. He never had any trouble with anyone."

Hernandez said she last saw her friend last week.

"He was just walking around with my nephews," she said. "Everything was fine."

Investigators are asking for the public's help in determining what happened. Anyone with information is asked to call Detective Czar Valdehueza at 510-675-5354 or the Union City Tips Line at 510-675-5207.