Kyron Horman: Missing Boy's Mother Files $10 Million Lawsuit Against Stepmother

June 2, 2012— -- Desiree Young, the mother of missing Oregon boy Kyron Horman, filed a $10 million civil suit against his stepmother Friday seeking answers about her son's disappearance.

"I believe that Terri Horman knows where Kyron is. I believe that Terri Horman is responsible for where my son is," Young said.

Police have pointed a finger at the boy's stepmother, Terri Horman, and have indicated there are discrepancies in her account of what happened on the morning of June 4, 2010, when Kyron disappeared.

Horman also admitted to hating her 7-year-old stepson, police said.

Kyron disappeared on the morning of June 4, 2010 after Horman attended a school science fair where her stepson had displayed a project on red tree frogs.

She said she last saw Kyron walking down a hallway toward his classroom.

When Kyron didn't come home on the bus that Friday afternoon, his parents called the school, which in turn called 911, launching one of the largest search operations ever in Oregon.

Police have since spent 28,000 man hours searching for Kyron.

"The time has come for Terri to take responsibility for what she has done and to tell me and my family where Kyron is and how he got there," Young said on Friday.

The missing boy's father, Kaine Horman, has since filed for divorce from Horman after being told she had allegedly tried to hire someone to kill him.

Terri Horman has remained steadfastly silent through most of the investigation, only releasing brief statements through her attorney that she did not have anything to do with Kyron's disappearance.

Her lawyer, Stephen Houze, said last year that his client had received death threats and that the media frenzy surrounding the case had morphed into a "witch hunt."

Nearly two years later, Kaine Horman and Desiree Young say they won't ever rest.

"Kyron, we will never stop, we will never give up," Young said. "I promise."