Leftists with guns aren't all that unusual. There's Mao, Stalin, Hitler, Pol Pot, Castro, Che, Lee Harvey Oswald . . . and just about every other whack job involved in a political assassination attempt or success in the last century or so.
Sane leftists with guns, however, would be unusual. Liberalism is a mental illness and mentally ill people have no business owning guns.
Plus, I should add, leftists are just about every other whack job involved in a mass murder attempt or success in the last century or so. Recent examples include Sandy Hook, the collateral damage from the attempt on Congresslady Giffords, the Aurora, Colorado Theater, Major Hassan at Fort Hood (still above ground and drawing a salaray for some unexplained reason) . . .
Need I go on?