The New York Times has this background: there doesn't appear to be anything related to politics here, this is all about having a vendetta against them as regards them publishing about his serious harassment of a woman for which he ended up in court. He clearly has anger management issues:

Who Is Jarrod Ramos, the Suspect in the Annapolis Newsroom Shooting? By Timothy Williams & Amy Harmon

[....]A Long-Running Dispute With The Capital

His feud with The Capital, the chain’s daily newspaper, apparently began with a column in 2011 that detailed his alleged harassment of a high school classmate.

After Mr. Ramos reconnected with the classmate in 2009, his emails to her soon turned venomous.

“He seems to think there’s some sort of relationship here that does not exist,” the woman told a judge, according to court documents in a harassment case she brought against Mr. Ramos. “I tried to back away from it, and he just started getting angry and vulgar to the point I had to tell him to stop.”

After she told him not to contact her again, Mr. Ramos wrote in a 2010 email that the woman should “go hang yourself.”

Weeks later, the woman was put on probation at the bank where she worked. A supervisor told her it was because Mr. Ramos had sent an email — and had also called the bank — telling managers that the bank should fire her.

As recently as 2012, Mr. Ramos worked for the federal Bureau of Labor Statistics. He has a degree in computer engineering.

A judge gave Mr. Ramos a 90-day sentence, but suspended the jail time. Instead, Mr. Ramos was granted probation before judgment. He was ordered not to contact the woman and to continue getting therapy.

Not long afterward, The Capital published the column that apparently fueled his anger.

A Losing Court Battle

Mr. Ramos filed a lawsuit against the owners of The Capital in 2012, claiming that it had defamed him in reporting that Mr. Ramos had pleaded guilty to a misdemeanor criminal harassment charge. Months later, he filed a fuller complaint alleging invasion of privacy, but the lawsuit was dismissed by a judge the next year because Mr. Ramos was unable to describe how he had been harmed by the newspaper article.

Mr. Ramos, who represented himself in the case, appealed the decision. But in 2015 an appellate court affirmed the lower court’s dismissal of the lawsuit, stating that Mr. Ramos showed little knowledge of defamation law and seemed not to “have learned his lesson.”

[....]

more "it's a new Trump on the press"

Of course, one could argue that the day-to-day flip-flopping lying and prevaricating Trump is the real Trump, past present and future.