White House Correspondents’ Dinner shooting suspect Cole Allen said he was shocked at how little scrutiny he got on his cross-country journey to kill Trump administration officials.

“Like, I expected security cameras at every bend, bugged hotel rooms, armed agents every 10 feet, metal detectors out the wazoo,” the 31-year-old wrote in an anti-Trump manifesto obtained by The Post that was sent to his family 10 minutes before the attack.

He said what he got instead was “nothing,” even raising the possibility he was being pranked.

“No damn security. Not in transport. Not in the hotel. Not in the event,” he wrote, alleging he noticed a “sense of arrogance” about the security situation when he arrived at the Washington Hilton on Saturday.

“I walk in with multiple weapons and not a single person there considers the possibility that I could be a threat,” he wrote.

“The security at the event is all outside, focused on protestors and current arrivals, because apparently no one thought about what happens if someone checks in the day before.

“Like, If I was an Iranian agent, instead of an American citizen, I could have brought a damn Ma Deuce in here and no one would have noticed s–t. Actually insane,” he wrote, invoking a nickname for the M2 Browning .50-caliber machine gun.

Follow The Post’s live updates on the shooting at the White House Correspondents’ Dinner

Acting Attorney General Todd Blanche said on “Fox News Sunday” that federal investigators believe Allen traveled from Los Angeles to Washington, DC, by train, with a stop in his native Chicago.

He said it was possible he chose train travel due to a less strenuous security environment than he would have encountered if he traveled by air.

Allen entered the hotel armed with a shotgun, a handgun and multiple knives around 8:30 p.m. before sprinting toward a security checkpoint. He exchanged gunfire with agents but was subdued and arrested.

This is a developing story. Please check back for updates.