Harley Watson was struck outside Debden Park High School in Loughton on Monday.
The families of the victims have been told, police said.
Essex Police have confirmed they are working with Vietnamese authorities, however are not yet able to confirm the victims' nationality.
It is feared such a group could be behind the 39 people found dead in Essex this week.
Three men and one woman remain in police custody.
11 of the Chinese nationals found dead have been transported to a hospital in Chelmsford.
As 39 people are found dead in a lorry in Essex, attention will once again be paid to the safety of migrants who risk their lives travelling to the UK via undocumented and dangerous means.
Discovery follows 39 dead bodies being found in a lorry container in Essex.
A 25-year-old man from Northern Ireland has been arrested on suspicion of murder.