Jacob Schwartz is also president of the Manhattan Young Democrats. View Full Caption Facebook/Jacob Schwartz

NEW YORK CITY — A city Build It Back employee and leader of a club for young Democrats was arrested Thursday for having thousands of pornographic images of infants and young girls on his computer, police said.

Jacob Schwartz, 29, turned over his laptop to police on March 29 — where investigators found more than 3,000 photos and 89 videos of nude girls as young as 6 months old engaging in sexual conduct, police said.

The oldest girl in the videos was 16, according to officials.

Schwartz works with the Department of Design and Construction on the city’s Build It Back recovery program, according to a now-deleted online bio and officials.

He’s also the president of the Manhattan Young Democrats, and founded a climate education nonprofit called Common Climate.

A spokeswoman for the DDC said Schwartz was hired as a temporary computer programmer analyst in 2015. He was fired on Friday, officials said.

“Obviously, these are extremely serious allegations. This is a junior-level agency employee with no connection to the Mayor or City Hall," said spokeswoman Melissa Grace in a statement. "The agency is cooperating with investigators.”

His lawyer, James Roth, said they're "going to be investigating the facts and circumstances surrounding the case."

Police traced an internet post back to Schwartz using an IP address, and conducted forensic tests on the computer, Roth said.

His client was arrested Thursday after calling police to see if he could get his computer back. They told him to come in before work — and then arrested him, his lawyer said.

Schwartz was arraigned later that day and released on $7,500 bail.