An 11-year-old boy crashed a pickup truck into a group of monks on a pilgrimage walk in northeastern Thailand on Thursday, killing eight, officials said.

A total of 35 monks from Mukdahan province, about 600 kilometers northeast of the capital Bangkok, were on the pilgrimage.

Five monks were killed at the site, while three others died at a hospital, according to Mukdahan Governor Worrayan Boonnarat. Fourteen others were hospitalized, with four in critical condition.

The group started the 260-kilometer walk to Ubon Ratchathani province about 30 minutes before the crash.

Security camera footage shared by a local rescue group, Ruam Jai Mukdahan Rescue Association, shows the monks walking in a single line on the side of a road before the truck crashes into them.

Local police said the boy is now in custody and will be questioned when state child protection officers arrive.

The police said the cause of the accident is still under investigation, but said they were told by the monks that they saw the vehicle swerving before it slid off the road and crashed into the group. (CNN)