An FBI document may confirm that the woman who helped carry out a shooting at a community center in San Bernardino, California, that left 14 people dead earlier this month did, in fact, pledge allegiance to ISIS while the attack was ongoing.

The FBI arrested on Thursday a friend of the married couple who carried out the shooting, and the FBI affidavit discloses some of the evidence the government has against the friend, Enrique Marquez, Jr.

In the document, the FBI notes that after the December 2 attack started, a post on a Facebook page associated with Tashfeen Malik read: “We pledge allegiance to Khalifa bu bkr al bhaghdadi al quraishi.” The FBI agent noted that he believes the post is referring to Abu Bakr al-Baghdadi, leader of the terrorist group ISIS — aka the Islamic State, ISIL, and Daesh.

The morning of December 2, Malik allegedly searched social media for “materials related to” ISIS, according to the FBI affidavit.

The attack started at about 10:58 a.m. local time, and the Facebook post appeared at 11:14 a.m.

Authorities have charged 24-year-old Marquez, a former neighbor of the couple, with conspiring to provide material support or resources to terrorists. Marquez is suspected of buying the rifles used in the attack and plotting terrorist attacks with the male shooter, Syed Rizwan Farook, in 2011 and 2012.

Farook, a US citizen, and Malik, who came to the US from Pakistan to marry Farook, opened fire on the Inland Regional Center, a county facility that provides services to the disabled.

Investigators reportedly believe that Malik also expressed jihadist sympathies online before she was approved for a US K-1 visa, but those messages were likely sent privately to a small group of friends in Pakistan, where authorities believe Malik was radicalized.

Though there isn’t clear evidence pointing to ISIS ordering and coordinating the San Bernardino shooting, it appears that Malik and Farook supported the terrorist group and carried out the attack in its name. This underscores the danger of terrorists who aren’t plugged into established networks and can therefore fly under the radar and remain undetected by authorities.