New Zealand's prime minister vowed Monday to unveil gun law changes within a week and called on gun owners to surrender their firearms to police after last week's shooting rampage that left 50 people dead.

"Within 10 days of this horrific act of terrorism, we will have announced reforms, which I believe will make our community safer," Prime Minister Jacinda Ardern said.

Ardern promised a review into security agencies after the mosque shootings, the New Zealand Herald reported.

New Zealand Police Commissioner Mike Bush said his officers would willingly accept guns from anyone who wanted to get rid of them. He suggested that people alert police ahead of time "given the current situation."

Ardern said she "applauded" people who handed in weapons and encouraged more to do so. Some gun owners took to social media to share stories of giving up their semiautomatic rifles. John Hart, a farmer and Green Party member from the Wairarapa, said on Twitter he had owned a gun for 31 years.

"On the farm they are a useful tool in some circumstances, but my convenience doesn’t outweigh the risk of misuse," Hart tweeted. "We don’t need these in our country."

The New Zealand auction website Trade Me said it was pulling semiautomatic weapons from its sites. Trade Me CEO Jon Macdonald had previously argued that his site was a better venue for dealing in weapons than more nefarious alternatives.

"But it is clear public sentiment has changed in relation to semiautomatic weapons, and we acknowledge that, which is why we're putting this ban in place," Macdonald said.

Gun City, a Christchurch gun shop, said Monday that it sold four guns to the accused shooter online since November 2017. “We detected nothing extraordinary about the license holder,” store owner David Tipple said. Two of the guns used were semiautomatic weapons that had been modified.

Monday, the man accused in the shooting, Brenton Tarrant, fired his lawyer and wants to represent himself at trial, the court-appointed lawyer said.

Richard Peters said the accused killer expressed no condolences or regret in the brief time they spent together.

"What did seem apparent to me is he seemed quite clear and lucid, whereas this may seem like very irrational behavior," Peters told the Herald. "He didn't appear to me to be facing any challenges or mental impairment, other than holding fairly extreme views."