In Nevada, where a school shooting school shooting today left two dead–including the shooter–and two injured, the governor vetoed a bill last June that would have strengthened background check laws.

Gov. Brian Sandoval, a Republican, rejected the measure despite an advertising blitz by the pro gun control group funded largely by New York City Mayor Michael Bloomberg, Mayors Against Illegal Guns.

The pro-gun control group advertised early and often Las Vegas this year, according to a search on Political Ad Sleuth, the Sunlight tool that tracks spending on political ads. Ads began in March and the most recent one aired in July on a local CBS affiliate, after the veto. Among the ads aired by the group was this one, captured by Sunlight's Ad Hawk tool, urging Sandoval to sign the bill. Earlier the group had run an ad urging the state senate to vote in favor of the bill.

Recently Talking Points Memo reported that Mayors Against Illegal Guns was considering Nevada as one of the states it may target for more spending in the upcoming year, either to defend the bill's sponsor, state Rep. Justin Jones, a Democrat, from in a possible recall election, or to punish lawmakers who voted against the background check bill.

Bloomberg personally contributed to political committees that supported two Colorado state legislatures who faced recall races last summer after they supported new gun laws in that state; they both lost their seats.