When Cesar Altieri Sayoc was arrested Friday, accused of sending at least 13 mail bombs in recent days to prominent critics of President Donald Trump, a glimpse of the Florida 56-year-old’s white van seemed to offer the most immediate insight into his motivations.

The van’s windows were blanketed with pro-Trump decals, alongside images of prominent Democratic figures that were unflattering, at best, or literally in the crosshairs of a red target, at worst. Other stickers blared “Dishonest Media” and “CNN sucks.”

On Twitter, Sayoc trafficked conspiracy theories and ranted about liberal billionaire George Soros, former president Barack Obama, former Secretary of State Hillary Clinton and others whose politics were out of line with his.

But nearly two decades ago, when Miami attorney Ronald Lowy first met Sayoc to represent him during some legal troubles, Lowy said Sayoc struck him as an insecure man, “like a 14-year-old in an adult’s body,” who was obsessed with bodybuilding and nightclubs — and who had no interest whatsoever in politics.

Lowy told CNN’s Anderson Cooper on Friday that Sayoc’s father had abandoned the family when Sayoc was young and that, in his opinion, Sayoc had struggled with identity issues as a result.

“This was someone lost,” Lowy told Cooper. “He was looking for anything, and he found a father in Trump.”

Despite his former political apathy, Sayoc quickly latched onto Trump as he emerged on the political stage and ultimately became president, said Lowy, who is now representing Sayoc’s family members.

“It’s my opinion that he was attracted to the Trump formula of reaching out … to these types of outsiders, people who don’t fit in, people who are angry at America, telling them that they have a place at the table, telling them that it’s OK to get angry,” Lowy told Cooper.

“I believe that that was a motivating factor. Do I blame the president solely?” he added. “No, this is a sick individual. I actually blame all of us. We have to start arranging for treatment when we start to see the problems.”

Lowy told The Washington Post he is representing Sayoc’s mother, Madeline Giardiello, and sisters Sabrina and Tina.

Giardiello, 76, has been active in Democratic politics and was an officer on her condominium board in Aventura for many years, Lowy said. She has not spoken to her son in three years, and he never showed an interest in politics when he and his family were last in touch, Lowy said.

“They are overwhelmed with grief over this,” Lowy told The Post. “No one should have to receive these threats and devices, whether operable or not. And they’re sad for a child and brother who is so sick and apparently involved in this crazy activity.”

Lowy said he represented Sayoc on a number of matters over the years, which he called “unsophisticated, stupid stuff.” He believed Sayoc was mentally ill and lived out of his vehicle for over a decade.

“He lives in a fantasy. I have no doubt he’s mentally ill,” Lowy said.

Sarah Jane Baumgartel, an attorney appointed Friday to represent Sayoc, declined to comment.

As questions swirled in the wake of Sayoc’s arrest, those who knew him described Sayoc as a disturbed individual who became fixated on Trump’s critics in a politically charged climate.

“I think this is a post-Trump sort of enticing somebody who maybe had some deep-seated issues, and this recent political climate seems to be bringing it to the surface with some people,” said Daniel Lurvey, a lawyer who represented Sayoc in the past.

One of Sayoc’s cousins, who spoke on the condition of anonymity, said Sayoc was “a really good guy who wouldn’t want to hurt anyone,” and the bombs — which didn’t detonate — were “a hoax.”

“This was his way of getting attention,” the cousin said. “He just wanted to get his opinion out there.”

The cousin said that while he did not know Sayoc to be political, he could intuit his relative’s message.

“He was saying you can’t speak against the president,” the cousin said. “The next guy who says we want to kick them when they’re down, he’s going to learn not to say that.” The cousin said that was a reference to Holder’s quipping at a recent campaign event, “When they go low, we kick them.”

Sayoc was no stranger to law enforcement, racking up several arrests for larceny, fraud and drug possession. In 2002, police in Miami charged Sayoc with calling Florida Power & Light and threatening to blow up the electric utility. The report claims Sayoc said “it would be worse than Sept. 11.” He ultimately pleaded guilty and was sentenced to probation.

Discussing an arrest for a bomb threat in a later deposition, Sayoc said he was “joking around,” but that the bomb squad had showed up at his dry-cleaning store.

Lawyer David McDonald, who questioned Sayoc for the deposition, said Sayoc was “glib and articulate,” but also “maybe delusional.”

“He described himself at the center of all these business ventures with all these people. It didn’t seem like it could be true,” McDonald said.

Another cousin, Lenny Altieri, 67, said Sayoc had worked for years at various adult entertainment clubs in South Florida.

He last saw Sayoc at a holiday gathering five years ago, and he said Sayoc sent some racist texts to him afterward.

“He didn’t discuss politics. This had to be when Trump got in, very recently, that he lost his mind,” Altieri said.

He added that his cousin was “built like a freakin’ animal. He took too many steroids, and they make you crazy.”

Sayoc’s support of Trump seemed to predate the election: He tweeted his support of Trump and his presidential campaign as far back as May 2016. At one point, a video clip shows, Sayoc attended a Trump rally.

He seemed to be fixated on Trump’s opponents. One account in his name mentioned Soros 34 times, Obama 29 times and Clinton 21 times over the years.

Of Holder, to whom authorities say Sayoc sent a package, the Florida man once wrote: “This man murdered for political reasons and got away with it.” The charges against Sayoc assert that he posted a message critical of Soros as recently as Wednesday. That was after authorities had recovered the package directed to the billionaire.

Sayoc, a registered Republican who lives in Aventura, Florida, north of Miami, attended Brevard College in North Carolina, where he was a member of the soccer team, according to a school yearbook. He also was listed as a member of the Canterbury Club, a religious organization. A yearbook photo showed him posing behind someone in a bishop’s robe.

Sayoc had worked in recent years as a pizza delivery driver. He claimed in a 2014 deposition that he had been a manager at a strip club called “Stir Crazy,” owner of a dry-cleaning store, a pro wrestler, a Chippendales dancer, a professional soccer player in Milan, and an arena football player in Arizona.

That work history, though, seems to have been inflated. Chippendales denied he was ever affiliated with the company. He also told co-workers that he was an American Indian from the Seminole tribe, that he lived on the reservation, and that he had done work for the Seminole Hard Rock Hotel & Casino in Hollywood, Florida. But the Seminole Tribe of Florida, Seminole Gaming and Hard Rock International said they could find no evidence to support that. His cousin said Sayoc’s father is Filipino and his mother is Italian.

Gureghian, the general manager of New River Pizza and Fresh Kitchen, said that Sayoc worked as a delivery-truck driver for several months but quit in January. The white van he drove to deliver pizzas was covered in disturbing images, she said, so the restaurant required him to park it on the side where it could not be seen.

“It was puppets with their heads cut off, mannequins with their heads cut off, Ku Klux Klan, a black person being hung, anti-gay symbols, torchings, bombings, you name it, it was all over his truck,” Gureghian said.

Sayoc was kept on because he did his work reliably and good drivers are hard to find, she said. But he disturbed his co-workers with racist comments and texts, she said.

“He was very angry and angry at the world, at blacks, Jews, gays,” she said. “He always talked about ‘if I had complete autonomy none of these gays or these blacks would survive.’ … He was very, very strange.”

Gureghian, who is lesbian, said that Sayoc made constant remarks about her sexuality.

“He used to tell me all the time that I was deformed and Jesus made a mistake in me,” she said.

She said Sayoc quit in January and told her he had trained to be a truck driver hauling hazardous materials, with a “top secret” clearance.

“He would categorize himself as a white supremacist,” she said. “He would just say, ‘Take back the world. That’s what he would always say, ‘Take back the world.’ “