Although festival organizers had effective control of the street, the permit required that it be operated according to the usual traffic control plan; organizers did not therefore have a duty of care that might have prompted them to change that.
Similarly, negligence per se, implied warranty, and public nuisance don't state a claim.
Murderous driver not sufficiently foreseeable; the test is forseeability from recent events, not actual knowledge of threat.
http://www.ca5.uscourts.gov/opinions/pub/17/17-50674-CV0.pdf
Since 2011. An occasional commonplacing of the U.S. Circuit Courts of Appeal.
Neither an authoritative statement of the law nor legal advice. Quick work.