Why Were The Fed's Involved?

From the LVRJ: Abdul Howard, a career criminal known as the “Cinched Hoodie Robber,” was sentenced to 13 consecutive terms of life in federal prison Thursday for a series of armed convenience store robberies during a 2013 crime spree.
Howard, 49, who is awaiting trial in Clark County District Court on murder and sexual assault charges, shot a store clerk in the neck, seriously wounding him, in one of the robberies.
Chief U.S. District Judge Gloria Navarro said she had “no problem” putting Howard behind bars for the rest of his life.
“You are an extremely dangerous man,” she told Howard, adding she wanted to make sure the impact on the victims of his crime spree weren’t forgotten....
Following an 11-day federal trial, Howard was convicted in June of all 27 counts stemming from 14 armed robberies during the crime spree. One of the robberies occurred at a small casino. The jury found him guilty of 14 felony counts of interference with commerce by robbery, 12 counts of possession of a firearm in furtherance of a crime of violence, and one count of a felon in possession of a firearm.  http://www.reviewjournal.com/news/las-vegas/hoodie-robber-gets-13-life-terms-prison
For the record, I am glad the thug is off the streets.
However, why were the Fed's involved?  These charges could have and should have been tried in the Nevada court system.
If you took it to the extreme, anyone busted for shoplifting could be prosecuted under "interference with commerce by robbery" by the Feds.
All the charges he was convicted of could have been brought into State court to be tried by local jury and sent to a local prison.
The Clark County DA and Las Vegas Metro are getting lazy and they are giving more control to the Feds, and that is not a good thing.
Ironically, the Feds will interfere in this case but they refuse to prosecute 99% of the illegal aliens who live in the U.S..