efe-epaChristchurch, New Zealand

New Zealand's police chief confirmed Monday that they believe that the perpetrator of a deadly attack on two mosques in Christchurch, that left 50 people dead, had acted alone.

The Australian Brenton Tarrant had opened fire on people at the Al Noor and Linwood mosques on Friday, in which another 50 people were wounded, of which some 30 remain hospitalized, including 10, who are in a critical condition.

"There is no indication at this stage that anyone else was directly involved in the attack - we believe this horrific act was committed by one person," Police Commissioner Mike Bush said at a press conference.

Bush revealed that around 250 experts, aided by the Federal Bureau of Investigation of the United States and the Australian Federal Police, were probing the attack, that is considered to be the worst mass killing in the country until date.

"The national threat level remains high, and our vigilance and visible presence will continue at this time. This is precautionary and for the safety and reassurance of everyone," Bush added.

Earlier during the day, Australia's anti-terror police had raided two houses belonging to Tarrant's sister and his mother's partner, in the eastern coast of Australia.

Tarrant was charged on Saturday with murder and will remain in custody until his next appearance before the High Court on Apr. 5.

Tarrant, a 28-year old former physical trainer, had broadcast the shooting live on Facebook.

Two other people were held in connection with the incident, including an 18-year-old, who was charged under the Films, Videos, and Publications Classification Act of 1993 for distributing the footage of the shootings.

He was also charged for posting miscellaneous material a week before the attack took place, including images of the mosque with the words "target identified", and messages inciting violence.

The other detainee was an armed man, who was arrested from inside his car near the police cordon around one of the mosques, and has been charged with possession of weapons.

However, the police do not believe that either he or the 18-year-old were involved in the attack.

Facebook said on Sunday that, during the 24 hours after the terror attack, it took down 1.5 million videos around the world, including 1.2 million that were blocked once they were uploaded.

In response to the attack, the worst in the country's history, the government on Monday announced "in principle decisions" to reform New Zealand's gun laws.