Investigators said a West Virginia two-time convicted felon, suspected of killing his ex-girlfriend and three men before committing suicide last week, bought his gun through Facebook around a year ago.

The ATF said the man was able to purchase the handgun in a private sale after contacting a poster advertising the gun on social media. The ATF advised that the seller is not currently facing charges, because he/she did not know the buyer was a prohibited person, a key requirement for prosecution.

But Facebook won’t even let legitimate, licensed gun dealers advertise legal, empty gun safes and other non-weapons on their FB pages, or allow pro-gun groups to have a page.