The group were unsuccessful in getting inside, he said.
"Police attended but were unable to locate this group."
Anyone with information about the group or who saw them in Burns St this morning is urged to phone Cambridge police on 07 827 5531.
Ruddell said St John staff were out there trying to look after the community and didn't need this sort of harassment.
"Ambulance staff are out there doing purely good work for the community and shouldn't be harassed or targeted in this way."
Stuart Cockburn, district operations manager for St John, saidSt John did not tolerate any kind of harassment or abuse towards staff and took staff safety very seriously. This incident was immediately reported to police.
"We are supporting our officer and working with Police on their investigation."