Who slaughtered the Passover lamb?

Ezra 6:20 (ESV)

20 For the priests and the Levites had purified themselves together; all of them were clean. So they slaughtered the Passover lamb for all the returned exiles, for their fellow priests, and for themselves.

In Exodus 12:6 it was the members of the community of Israel that slaughter the Passover lamb. In Ezra 6:22, it is the Levites. During the course of the Old Testament, it seems as if this task was also done by the Levites to help the people.