(CNN) -- Four months after a criminal investigation began into the disappearance of an Oregon boy, officials continue to ask the public for leads and tips.

Thursday marks Kyron Horman's 8th birthday. Desiree Young, Kyron's biological mother, said she will celebrate the birthday by releasing red balloons outside a church in Medford, Oregon.

His stepmother, Terri Horman, said she dropped him off at Skyline Elementary School on the morning of June 4. She has been the subject of intense scrutiny for several months.

In divorce filings, her ex-husband, Kaine Horman, said he believes that Terri Horman "is involved" in the boy's disappearance.

Court documents also allege Terri Horman attempted to hire a man to kill her husband.

Meanwhile, Skyline Elementary began its first day of classes for the year on Tuesday with additional security measures to protect the children and staff.

In a letter to parents, Principal Ben Keefer said video cameras will be installed this weekend at Skyline.

"These cameras will show external views of the building as well as the main hallway," he wrote.

Also, security procedures will be reviewed to ensure they are effective, he added.

Tributes, messages, posters and cards that adorned a "Wall of Hope" for Kyron were moved from school property to a fence outside a nearby fire station, said the Multnomah County Sheriff's Office.

"We're happy that the fire district can provide this service to the community," said Tualatin Valley Fire & Rescue Communications Officer Brian Barker. "Our hearts go out to Kyron's family and we all hope for a positive resolution to this case."

1. Who was kidnapped?
2. Who dropped him off at school?
3. Who does she say could be the suspect?
4. Who tired to murder him?
5. What was placed for him at the school?
1. Kyron Horman
2. Terri Horman
3. Terri Horman
4. Terri Horman attempted to hire a man to kill her husband.
5. "Wall of Hope"