The Office of Homeland Security and Memphis police questioned a suspect Sunday after the New York Police Department issued a warning to officers that a man was driving to New York from Tennessee to kill two more police officers, Fox News has learned.

Homeland Security questioned the suspect at his home and released him, according to an email from the Memphis Police Department in response to a FoxNews.com inquiry.

The initial warning, issued via a text message to NYPD officers Sunday afternoon, comes one day after a gunman ambushed and murdered two police officers -- Rafael Ramos and Wenjian Liu -- as they sat in their patrol car in Brooklyn. The gunman, Ismaaiyl Brinsley, 28, fled to a nearby subway station, where he shot himself in the head and later died.

The NYPD text alert, obtained by FoxNews.com, shows a photograph of a young man, and displays his name and birth date. Fox News is withholding the information pending confirmation by the NYPD.

The man sent the threat on Instagram, Officer Arlene Muniz, an NYPD spokeswoman, told FoxNews.com.

“We are aware of the threat,” said Muniz. “We are aware of it and are investigating,” she said prior to the response by Homeland Security.

Meanwhile, the NYPD is searching for a Brooklyn man who threatened cops by posting an online photo of a man firing into a marked police car, which appears to be taken from a movie, law enforcement sources told the New York Post.

Devon Coley, 18, wrote the message "73Nextt”on his Facebook Page Saturday in an apparent reference to the 73rd precinct in Brooklyn where he lives. Authorities are also considering charges against Coley, the source added.

Brinsley, 28, wrote on his Instagram account: "I'm putting wings on pigs today. They take 1 of ours, let's take 2 of theirs," hours before the killings, two city officials with direct knowledge of the case confirmed for The Associated Press. He used the hashtags Shootthepolice RIPErivGardner (sic) RIPMikeBrown.

The post also included an image of a silver handgun and the message, "This may be my final post. The post had more than 200 likes but also had many others admonishing his statements.

The New York Post reported that the handgun recovered at the scene of the shootings matches the one posted to Brinsley’s Instagram account.

A second Instagram post dated just after the shooting showed the same camouflage pants and distinctive blue sneakers worn by the gunman as his body was carried from the scene on a stretcher.

Fox News’ Edmund DeMarche contributed to this report.