Laws don't deter tragic shootings
As for "high powered" that round is not legal on deer-sized game in most states, including Washington. We have over 25,000 laws in America regulating the transfer and use of firearms. None of them prevented any shootings, nor would any new laws, as would be expected once you understand that laws only deter the law-abiding!
For the record, every gun show member undergoes an ATF background check and no one but a member can trade in firearms. The "gun show loophole" is a malicious fiction, a knowing lie of the gun grabbers. Since the National Firearms Act in 1934 provided for licensing owners of fully automatic firearms not a single licensee has committed a felony or serious crime, as far as I can determine. What other group can make that claim after nearly 80 years!