In a post for Autism Speaks, Danny Oquendo thanked the city for helping search for his brother.
Volunteers continue to search for the missing autistic teen, who was last seen Oct. 4.
NYPD Commissioner Ray Kelly told a news outlet he's not sure Avonte Oquendo will be found alive.
Volunteers were using kayaks to scour the shoreline while police are expanding their search.
The reward for the return of Avonte Oquendo has been increased to $70,000.
Avonte Oquendo's family is planning to file a lawsuit against his school for letting their son leave.
Avonte Oquendo, of Rego Park, was last seen on Friday in Long Island City.
Avonte Oquendo, who cannot speak, was last seen on Friday.
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