Oh i only had this happen once with my four year and i didnt know what to do either we were at a bus stop for about 30mins with her screaming, crying hitting, kicking me and this continued on the bus she was still making loads of noise and wouldnt sit down at all (she actually made me cry at one point) until we were almost home. I just ignored her totally, other people dont help either do they making little comments such as "if that was my child......"
But Ignoring (as long as they safe) is what worked for me then when we got home i told her to go to her bedroom for a awhile as she had really gone too far, i left her there for 10mins (i know its way to long but she had gone on for an hour long full blown tantrum i needed time to think too) then i went and got her and told how she had made me feel and how i
never wanted her to do anything like that again i was firm with my voice and really explained what i didnt like and why i didnt want it to ever happen again and touch wood it didnt.
If this has gone on for a little while already and you chose to try ignoring i think it may a little time for him to realise its going to work anymore.
Good luck i hope he stops it soon what you do.