A QAnon-obsessed dad who allegedly shot dead his two young children with a spear gun at a Christian resort in Mexico pleaded not guilty to the gruesome murders in a California court.

The plea comes after Matthew Taylor Coleman, 40, admitted to the FBI that he killed his two young kids just days after the 'heinous, cruel and depraved' act, according to court documents.

Coleman had told the agents that 'he received visions and signs that his wife possessed serpent DNA and had passed it onto his children'. 

He will remain in an undisclosed federal prison - after prosecutors at the US District Court in San Diego argued Coleman is a flight risk and a danger to others or himself - until his next hearing, which is scheduled for November 5.  

Santa Barbara District Attorney Joyce E Dudley said his not guilty plea last Wednesday was expected, even with the FBI's testimony.

She told the  that 'a confession isn't the same as an admission of guilt'.

Last month, Coleman was indicted and charged with two counts of foreign first-degree murder of United States nationals after he took his two-year-old son Kaleo and 10-month-old daughter Roxy to a Christian ranch in Mexico to murder them. 

He told federal agents he used a spear fishing gun to shoot Kaleo and Roxy in the heart before dumping them in a field outside Rosarito. 

According to court documents, when they did not die right away, Coleman stabbed his son 17 more time and his daughter 12 more times, cutting his own hand in the process. 

The charges make him eligible for the death penalty. If the Attorney General decides against the death penalty, Coleman's maximum sentence would be life in prison with a fine of up to $250,000.

Coleman was represented by a public defender. 

While Coleman's wife Abby had no clue her husband was a QAnon follower, one of his childhood friends said that the alleged killer 'was constantly checking those sites on his phone'.

The friend, who spoke anonymously to

 'He spent hours each day just glued to his phone looking at that stuff,' he added.

Although the friend didn't know the exact websites Coleman frequently looked at, he said he would bring up QAnon theories throughout their conversations and say: 'Listen to this one'.

'He's show me other posts of other people who believed the strangest things,' the anonymous source told People.