Investigators believe that the man charged with the attempted assassination of President Donald Trump shot a Secret Service officer who was wearing a ballistic vest, according to three law enforcement officials familiar with the case.

Investigators have determined that the Secret Service Uniformed Division officer was not struck by friendly fire from another member of law enforcement, the sources told NBC News on Wednesday.

Cole Tomas Allen, 31, on Saturday allegedly charged a checkpoint one floor above the Washington Hilton ballroom where the president was attending a black-tie event for the White House Correspondents’ Association.

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Cole was caught on video running with a shotgun and other weapons. Officials say an officer was hit on his vest and returned fire.

The officer was taken to a hosptial but released over the weekend.

Allen was charged with discharging a weapon but has not been formally accused of assaulting a federal officer.

A law enforcement source said work continues analyzing Allen’s devices including desktop and laptop computers from his California home as well as his phone, laptop and hard drives recovered from his guest room at the Washington Hilton hotel.

Allen, a teacher and engineer from Torrance, California, made his first court appearance Monday and was charged with the attempted assassination of the president, interstate transportation of a firearm and ammunition with intent to commit a felony and discharge of a firearm during a violent crime.

Selfies that Allen took in his hotel room on Saturday night before the attack were included in a filing from prosecutors Wednesday. The photos showed him standing in front of his hotel room mirror wearing black and a red necktie.

According to the filing, the image showed the suspect “wearing a small leather bag consistent in appearance with the ammunition-filled bag later recovered from his person,” along with a shoulder holster, a sheathed knife, pliers and wire cutters.

Allen allegedly believed it was his duty to target Trump administration officials, according to a note he sent to family members minutes before he charged the checkpoint.

A transcript of the note provided to NBC News by a senior administration official showed that Allen apologized and said he didn’t expect forgiveness.

People who know Allen have described the one-time NASA intern as “borderline genius” and gentle person who was interested in coding and attended the California Institute of Technology, commonly known as Caltech, in Pasadena.

In an emergency filing Wednesday, Allen's federal public defenders said jail officials had not given them the opportunity to communicate with him in a way that protects his confidentiality. Within minutes, U.S. District Court Magistrate Judge Matthew Sharbaugh ordered that the city's corrections department allow Allen and his defense team to have unrestricted legal visits.