The deranged homeless man accused of stabbing two Museum of Modern Art employees on Saturday had attacked a man and threatened a union official after he was sacked from his job at a Broadway theater, police and sources said.

Gary Cabana, 60, has evaded police capture since he slashed two workers in a rage because he was told his membership had been revoked.

But by the stabbings followed two other disturbing incidents that came after he was let go from a job at the Nederlander Theater on West 41st Street, police sources said.

After Cabana lost his job, he sent threatening emails between November 2021 and January to a woman at the International Alliance of Theatrical Stage Employees office, which represents projectionists and ushers, cops said.

“Payback is coming,” he wrote to the woman, police said. “F–k you c–t.”

Police said he visited the union office on West 45th Street on two occasions, looking for the woman. She allegedly told police that she feared for her safety because he had assaulted a co-worker recently.

He was slapped with a criminal harassment complaint as a result of the allegations.

In January, Cabana allegedly punched his former manager in the face outside of the Nederlander, according to police sources.

Cabana had attempted to enter the theater with a ticket and hit the manager with a closed fist after he was escorted out, according to police sources.

A manhunt for Cabana remains underway since his violent attack at the MoMA.

On Monday, panic briefly erupted at a Manhattan church after a 911 caller told authorities he had seen Cabana go inside.

The call prompted the evacuation of St. Francis of Assisi Church on West 31st Street just before noon as police searched for Cabana pew by pew. Police sources told The Post they found a man that looked like Cabana, but it was not him.

“We’re looking for him,” the source added. “We’ll get him.”

The fugitive remains active on social media, posting bizarre ramblings that mentioned bipolar disorder and claimed the allegations were a “total frame job” by officials at the museum.

Cabana sent a series of direct messages to a New York Post employee on Sunday night, in which he claimed he “lost it” on Saturday when the MOMA employees refused to let him into the famed museum to see Van Gogh’s masterpiece “Starry Night.”

He blamed the victims for the attack, saying they conspired with a woman named “Barbara,” whom he claimed lied to get his museum membership revoked.

“The stabbed girls were in on the BACKSTABBING too,” Cabana wrote in his message. “I don’t backstab, I do the frontside only.”

He denied causing any disturbances at the museum in the two instances that led to the revocation of his membership. He said he was “completely blindsided” by a letter from the museum’s security director that said he was “aggressive [and] disruptive” on Feb. 24 and last Wednesday.

Cabana allegedly flipped out when he was turned away around 4 p.m. while trying to get into a screening of “Bringing Up Baby” at the museum, authorities said. Both victims — a man and woman, both 24 — were taken to the hospital with non-life-threatening injuries.