Unfortunately school violence can occur most anywhere across the country, and with Clark Co. now the 5th largest district in the US it's not going to be exempt. The school district had a recent assessment done by the National Association of School Safety and Law Enforcement Officers, one of the nation's oldest school safety and security organizations, since there were concerns just like yours.
The story about it was in the Las Vegas Review Journal. You'll find this organization's overall view of the Clark. Co. schools' student safety and security in comparison to the rest of the US near the bottom of the article.