The perpetrator of Saturday night’s explosion in the Chelsea neighborhood has yet to be determined, but police are piecing together several bits of information from witness reports and online postings.

The New York Post is reporting on a 911 call that law enforcement received shortly after:

“I’m looking at the explosion down the block. There will be more,” the unidentified male said, claiming to be standing at 23rd Street and Seventh Avenue in the aftermath of the terrifying incident, according to law-enforcement sources Sunday.

Investigators believe the blast was the result of a home-made, pressure-cooker bomb similar to an unexploded device found later on 27th Street, sources said.

In another new wrinkle, a hand-written letter, a portion of which is in Arabic, was found inside a plastic bag that held the second device, sources said.

Police are interviewing several people who were dining in a nearby bar and grill, when they spotted what they described as “an Arab-looking man,” who was carrying a suitcase and seemed out of place.

The police do have surveillance video of someone placing the second device, which was found, unexploded, by an older woman.

As for the online aspect, a blog post on Tumblr is being vetted by law enforcement.

The blog, posted under a picture of a rainbow flag, claimed to have been responsible for the explosion, and said “anti-gay violence and oppression” was the reason.

The blog title was: “I’m the NY Bomber: This will be my manifesto.”

“I did it because I cannot stand society. I cannot live in a world where homosexuals like myself as well as the rest of the LGBTQ+ community are looked down upon by society,” one post says.

It’s unclear whether it was law enforcement, or the author of the post, but as of Sunday morning, the post had been removed.