Bump stock owners have 30 days to turn in their devices after Gov. David Ige on Monday signed a law banning their sale, possession and manufacture. The law was spurred by last year’s mass shooting in Las Vegas in which a gunman fired into a concert crowd, killing 58 people and injuring hundreds within 10 minutes.

The gunman had modified his gun with a bump stock so that it would fire more rapidly. The new law bans bump stocks and other trigger- modification devices that allowed the gunman “to be horrifically efficient in what he was doing,” said Ige during a bill signing ceremony.

The law takes effect immediately, but county police departments have agreed to an amnesty period in which owners have 30 days to turn in the devices to a police station or call 911 and have a police officer pick them up. The new law makes it a felony to sell, possess, transfer or import to Hawaii bump stocks and other modification devices, including multiburst trigger activators and trigger cranks.

Hawaii is now one of several states that have banned bump stocks in recent months. On Monday, Ige also signed a bill that shortens the period that a gun owner who is disqualified from possessing a firearm has to turn in any firearms or ammunition to seven days from 30 days.

It’s not clear how many bump stocks there are in Hawaii, but as many as 520,000 have been sold nationally, according to estimates from the federal Bureau of Alcohol, Tobacco, Firearms and Explosives. The devices on average have sold for about $200.

Getting Hawaii residents to turn in the trigger-modification devices could be challenging. Under a similar law that was passed this year in New Jersey, residents were supposed to destroy or turn in their bump stocks by mid-April, but as of May, state police said they had yet to receive a single device, according to an article in Stateline, a publication of Pew Charitable Trusts. Other states have reported similar results.

The Trump administration is also in the process of banning bump stocks under federal law by amending Department of Justice rules.