ST. LOUIS, MO (KTVI - FOX2now) - St. Louis Metropolitan Police confirmed Tuesday that the decomposing body found in Cold Water Creek in Florissant Sunday afternoon is that of Antonio Calvin, 18, who has been missing for more than a week. Even though his alleged attacker was locked-up, there was new information suggesting the case might still be far from solved. The latest developments were taking an agonizing toll the family of 18 year old Antonio Calvin.

For the 12 days since he disappeared March 12th, Calvin's family longed to where he was; what had happened to him.

For 12 days Calvin's family has just wanted to know, where was he? What happened? Police believe they know who killed him, but there's no word on why. Calvin's loved ones said they believe the killer had help. Someone moved Calvin's body for him.

"Even though it seems like there couldn't be, there is some type of relief," said Calvin's sister, Sherrie Green.

Understand that every time there was news of a body being found, Antonio Calvin's family agonized over whether this time it might be him. Sunday, when kids found a body wrapped in a tarp in Coldwater Creek in Florissant, it wash. Calvin's mother told Fox 2 the body was positively identified Tuesday; DNA from the body matching hers.

"Somebody needs to say something and at least tell us what happened so we'll know. I don't know what to say," said Calvin's mother, Michelle Green, her voice fading to tears.

"The assault itself occurred in the 3100 block of Oregon [in South St. Louis]," said St. Louis Police Captain Michael Sack at a Tuesday afternoon news conference.

Police said they Todd Metcalf, 17, beat Calvin in the head with a ball bat March 12th, after Calvin got off from work at the Jack in the Box at Bayless and Union in South County. Metcalf surrendered the following night after a brief pursuit in Webster Groves.

Those living near the creek where Calvin's body was found miles away in Florissant, doubted Calvin's body had been there very long; someone would have noticed it before Sunday, they said. By the time someone did, Metcalf had already been locked up for more than a week.

"At some point [after the beating] the victim was taken to a different location, that subsequently being in Florissant at this creek," Captain Sack said. "That's what we're trying to see - if anybody has any information about what might have been seen that evening, how he was being moved and how he might have been placed in that creek."

"It seems like the crime rate is attacking our younger generation," said Sherrie Green. "We need to get through to them somehow so that nobody else has to sit here go through this," she cried, closing her eyes.

Metcalf remains locked up on charges of assault and armed criminal action. Authorities may charge him with murder once the medical examiner determines the cause of death.

Calvin's family is has set up a reward fund in Calvin's name at US Bank. You can donate at any branch.

Police are asking anyone with information to call CrimeStoppers at 866-371-TIPS.