Updated at 1:40 p.m. June 18: Revised to include information about the suspect's discharge from the military.

The 22-year-old man who opened fire Monday morning on the Earle Cabell Federal Building in downtown Dallas had shared images and a video of weapons on social media in recent days.

Brian Clyde is seen in two photos posted to his Facebook page, most recently in the one (right) posted May 8, 2019. Clyde opened fire at the Earle Cabell Federal Building in downtown Dallas.

Brian Isaack Clyde, who authorities confirmed was the gunman, served in the Army for two years. Soldiers who served with Clyde said he came from a family of military veterans and often participated in war re-enactments.

But in 2017, Clyde felt the military wasn't for him as he struggled with training and tests in preparation for possible deployment, they said.

Clyde was photographed with a large knife and multiple high-capacity magazines fastened to a belt as he opened fire on the federal building before 9 a.m. Monday.

Federal authorities leading the investigation have not offered a motive for his attack, which ended when he was fatally wounded during an exchange of gunfire.

FBI Special Agent in Charge Matthew DeSarno said Clyde was not on any federal watchlist or otherwise "of investigative interest."

An Army spokesman confirmed Clyde was a private first class and served as an infantryman in the Army from August 2015 to February 2017.

Clyde was honorably discharged from the military, an FBI spokeswoman said Tuesday. No further details about his discharge have been released.

'We lived with guns in our hands'

Dennis Bielby, 22, served with Clyde in the 101st Airborne Division, stationed in Fort Campbell, Ky.

He said Clyde struggled with the high stress of military life but was "kind and gentle."

Bielby said veterans, including himself, sometimes struggle with mental health issues as they're transitioning back to civilian life. But he said the shooting was inexplicable.

"In the military and the younger generation, it's very common to joke about suicidal depressive thoughts," Bielby said.

But he said he couldn't say for sure whether Clyde had made those sorts of jokes.

"Everyone makes those jokes," he said.

Bielby said that after Clyde was discharged in 2017, he didn't stay in close contact with him. When he heard the news of the shooting, Bielby thought immediately of a photo Clyde had posted on Facebook of several gun magazines two days before the shooting.

"2 40 rounders and 8 30 rounders total," Clyde wrote in the post.

But Bielby said that wasn't a red flag.

"We lived with guns in our hands," he said.

Matthew Newell, who also served with Clyde in Kentucky, said Clyde felt pressure to stay in the military but after 2017 wanted to look for a “new path."

“He didn’t want to let anyone down,” Newell said. “He was looking forward to finding another option.”

He said Clyde left the Army to enroll in school and find a job.

Newell said Clyde was a gun enthusiast who was fascinated with military history and medieval weapons.

Gabriel Wadsworth, who was stationed with Clyde at Fort Campbell in 2015, said, he was "still shaking" at the news.

Wadsworth said that he and Clyde exchanged messages on Facebook on Sunday night and that Clyde didn't share any information that worried him.

"Nobody knew that he would have done something like this," he said.

Military upbringing

Clyde, who did not appear to have any criminal history, had lived in Corpus Christi and Austin, public records show. It was unclear whether he was living in Dallas before the shooting, but records indicate he had relatives who lived in the area.

A man who answered the door at the Plano home where public records show Clyde's family lives declined to comment.

Reached by telephone Monday afternoon, Clyde's grandfather, Rodney Clyde, said he had "nothing to say at this time" and declined to comment further before he hung up.

In a video Brian Clyde posted on Facebook in which he appears to be receiving an outstanding student award from Del Mar College in Corpus Christi, he said he had served in the Army. Clyde's Facebook page was taken down Monday afternoon.

"Military has always been big in my family, so has education," he said. "When I got out, I really didn't have any other options, so I figure go to school."

He was one of 983 prospective graduates from Del Mar this spring, according to the school.

Clyde graduated from Leander ISD's Vandegrift High School in 2015. School district records indicated that he was a member of the JROTC program.

Prior to transferring to Vandegrift, Clyde attended Dallas ISD schools. He went to E.D. Walker Middle School and spent two-thirds of his freshman year at East Dallas' Woodrow Wilson High School.

Watch exclusive video from Dallas Morning News photographer Tom Fox, who witnessed the shooting:

Social media

Clyde posted frequently on Facebook, sharing political memes that made light of — among other things — incest and the Chernobyl nuclear accident. Several memes included Confederate flag imagery.

One meme he shared referred to a “Chad rampage” vs. a “virgin shooting” — the Chad vs. virgin trope is a common “incel” meme, which is short for “involuntary celibate.” The meme contrasted how two men — a "Chad" and a "virgin" — would go about carrying out a shooting.

In the memes, "Chads" are strong men who can attract women, unlike weaker "virgins."

The term "incels" usually refers to an online community of men who blame women for not having sex with them. In some cases, the internet subculture makes its way offline, such as when a man killed 10 people after he drove into a crowd in Toronto last year and pledged allegiance to the "incel rebellion."

On June 9, the day a sudden, violent storm blew through Dallas, Clyde posted a video to Facebook in which he is illuminated by candlelight.

"I don't know how much longer I have, but the [expletive] storm is coming. However, I'm not without defense," he says in the video, holding up what appears to be a rifle wrapped with duct tape. "[Expletive] ready. Let's do it."

In a post in April, he wrote, "God i love gun shows."

Staff writers Cary Aspinwall, Sarah Sarder, Dave Boucher, Kevin Krause and Corbett Smith contributed to this report.