Deputies responded a reported stabbing at 3:25 p.m., at a mobile home park on Shady Grove Road in Ruckersville.
WCAV reported that neighbors said the stabbing arose from an altercation over a juice box, but authorities have not confirmed that information.
"I always see him riding his bike and everything. He seems like a happy go lucky kid. No problem," said Nikoma Collins, a neighbor.
Sheriff Smith said the victims, two juveniles and one adult, were all taken to the University of Virginia Medical Center with non-life threatening injuries.
"I've heard of juveniles throwing temper tantrums, but I've never heard of anything like this before," Sheriff Smith told WCAV of the incident.
At least one victim is related to the child, but authorities have not revealed which one or the nature of that relationship.
Smith told WCAV that the 5-year-old is currently in police custody and is being evaluated.