Five year-old Kayden Fleck (right) with his twin brother Jayden (left).
Kayden fell into the Braid River in Ballymena, County Atrim in Northern Ireland, at around 1pm on Saturday.
A major search and rescue operation was launched and Kayden was pulled out of the river, before being airlifted to hospital.
A message from Kayden's school, Harryville Primary School, said it would be open today and tomorrow from noon until 6pm to allow anyone from Harryville, Ballykeel and wider areas to sign a book of condolence.
The family say they are grateful for the community support they have received since.
Sean McCarry, regional commander of the Community Rescue Service, said the boy "accidently fell into the River Braid near the Ecos Centre at Ballymena and was quickly swept downstream".
"The whole school community is remembering you at this sad time", they wrote.
"NIAS dispatched an A&E crew, a BASICS doctor and the Air Ambulance to the scene to assist in a multi-agency search and rescue for the boy".
Sadly, however, he was declared dead shortly afterwards.
He said rescue workers were "running desperately" after the youngster as a police helicopter reported sightings of the child.
He said: 'The police were co-coordinating and telling us where we needed to go to next and we were just trying to get ahead of him in the river.
At approximately 15.04pm, the child was found and pulled out of the river.