More from NBC News:
Complete Coverage of the NY/NJ Bombings
Ahmad Rahami, Suspect in N.Y. and N.J. Bombings, Charged With Attempted Murder
Ahmad Rahami: What We Know About N.Y., N.J. Bombings Suspect
The revelation about the note a day after the search for the 28-year-old suspect ended with a gun battle in Linden, New Jersey. The suspect and two police officers were wounded in the shoot-out.
In addition to the news of the note, here's what else we know so far:
- Rahami, a naturalized U.S. citizen from Afghanistan who lives in Elizabeth, New Jersey, was being held on $5.2 million bond as investigators continued to investigate the three-day bombing spree in New York City and New Jersey.
- The Rahami family first appeared on the FBI's radar two years ago after police responded on Aug. 25, 2014 to a report that he'd stabbed his brother in the left leg. Officers learned from a neighbor that the suspect's father, Mohammad Rahami, yelled at him, saying words to the effect of, "You're a terrorist. Get out of my house," two federal law enforcement officials told NBC News. Questioned by the FBI, the elder Rahami said he made the statement "out of spite" and that it was not true. The FBI, which had opened what's called an assessment, dropped the case. Also, the domestic violence charge against Rahimi was later dropped.
- Federal investigators revealed there were four explosive devices: One made from three pipe bombs that exploded Saturday in Seaside Park, New Jersey; two pressure cooker bombs, one of which went off in Chelsea on Saturday night and injured 29 people, as well as a "multi-part device" that was found Monday at a commuter rail station in Elizabeth. They do not yet know where the bombs were put together, but they know the flip phones used on the devices were bought at the same store last year.
- While investigators believe that Rahami was most likely a "lone wolf," they are still questioning five people who were in a "vehicle of interest" that police stopped Sunday near the Verrazano Bridge in New York City.
- Rep. Albio Sires, a New Jersey Democrat, told NBC News that Rahami sought help in March 2014 with getting a visa for a woman named Asia Bibi Rahami, who he claimed was his wife. It was denied because the woman was 35 weeks pregnant.
- Investigators were trying to determine whether Rahami was radicalized on trips to Afghanistan and Pakistan during the last decade. A senior U.S. intelligence official told NBC News on Monday that Rahami — who was 7 years old when his family sought asylum in America — visited his homeland as recently as April 2013 and that his older brother Mohammad is believed to still be living there.
- Rahami's former classmates at Edison High School in Edison, New Jersey, were struggling to reconcile the "cool dude" who graduated in 2007 with the suspected terrorist who is now charged with five counts of attempted murder of a law enforcement officer and likely to be hit with federal charges that could send him to jail for life.
Investigators zeroed in on Rahami after he was seen in surveillance footage taken Saturday night amid the mayhem in Chelsea.
The blast Rahami allegedly set off was so powerful that it sent a dumpster flying more than 150 feet down the sidewalk and shattered windows more than a block away. Police are not clear on why the second device found a few blocks away on 27th Street did not detonate.
Nor has the FBI revealed why the Chelsea neighborhood was targeted.
Sources told NBC News that a fingerprint linked Rahimi to one of the pressure cooker bomb — a potentially deadly device similar to the ones used by the Tsarnaev brothers during the Boston Marathon bombing on April 15, 2013.
Rahami was arrested by officials on Monday, hours after a backpack bomb he allegedly planted in near a train station in Elizabeth went off as a police robot examined it.
Mohammad Rahami, who operates a restaurant in Elizabeth called "First American Fried Chicken," has told reporters he had "no idea" what his son was allegedly planning