I've never tried K-2 or Spice so I have no personal experience with these products. From what I've read about others who have, reactions range from pleasant to adverse. Comprised of herbs that are sprayed with a chemical compound (such as JWH-018), they're sold in convenience stores and head shops around the country (wherever they have not been restricted), and proliferate among users who'd rather smoke a quasi-legal product that mimics marijuana and can be bought over-the-counter. Once marijuana is available in stores, these products would disappear altogether. They only exist because of prohibition.
Burnett's parents are currently on a media campaign to inform the public about what they call "death weed." They have reason to blame those products, but also need to see the big picture. It's doubtful they will. Their son is gone and they need to point fingers. They should be directing their anger at the federal government, which has outlawed non-toxic marijuana for more than 75 years.
Lift the ban on pot and so-called death weed will meekly go away. But until then there may be more mortalities to deal with. No one dies from marijuana.