Short answer, no. I don't think the new laws had any affect.

Long answer, if he was concerned with round count, even after the new laws he could have chosen a long gun with higher capacity than a shotgun. Pure speculation on my part, but cost could have been a factor. There are some VERY cheap shotguns. Just writing that makes me cringe though because if investigators somehow find he bought it because it was cheap, then I'm sure it will be only hours before some Saturday Night Special V2.0 Shotgun ban will be introduced.