San bernardino shootin tributes
Gary Mendoza and his son Michael Mendoza walk around a makeshift memorial near the Inland Regional Center as they pay their respects to those killed and injured on 7 December 2015 in San Bernardino, California. Law enforcement officials continue to investigate the mass shooting at the Inland Regional Center in San Bernardino that left 14 people dead and another 17 injured Joe Raedle/Getty Images

The Federal Bureau of Investigation (FBI) has said that the couple who murdered 14 people in San Bernardino last week practised their shooting at local shooting ranges just a week before the attack. Suspects Syed Farook and his wife Tashfeen Malik wounded 21 others in the attack which took place at an end of year party at a learning centre where Farook once worked.

The pair had left their six-month-old baby at home at the time of the massacre on 2 December. They were both killed just a few hours later in a firefight with police officers.

On 7 December David Bowditch, the FBI's assistant director in charge of the Los Angeles field office said that the pair had been practising with their weapons as recently as a week before the killings. He added that the FBI understood that they had been radicalised for "quite some time".

David Bowditch
David Bowdich(3-L) of the FBI briefs the press outside the San Bernardino Police Department on December 7, 2015 in San Bernardino, California. The husband and wife who killed 14 people in last week's shooting rampage in California were both radicalized and 'for quite some time,' the FBI official in charge of the investigation said Monday FREDERIC J. BROWN/AFP/Getty Images

He said: "We have learned and believed that both subjects were radicalised and had been for quite some time."

The attack has become the deadliest 'terrorist' incident on US soil since 9/11. The FBI added that they are still interrogating the grandmother of one of the suspects in an effort to determine if anyone else was involved in the planning of the offensive.

The Islamic State (Isis) claimed responsibility for the attack via their online radio station, al-Banyan. Malik, who was educated in Saudi Arabia and Pakistan before marrying Farook, was reported to have posted a message on Facebook in support of IS' leader under a different name around the time of the shootings.

Bowditch added that he doubted that there was no evidence, as of yet, that the attack was coordinated outside the US. He said: "I want to be crystal clear here, we do not see any evidence so far of an outside-continental-US plot. We may find it someday, we may not. We don't know."