New York ( CNN ) Nine men have been arrested in connection with alleged threats made toward New York police since Saturday afternoon , when two NYPD officers were shot in the head from behind while sitting in their patrol car , authorities said . Police said this week that they have assessed hundreds of online postings and calls to 911 and pressed the public to continue to report any suspicious activity . `` All threats against members of the NYPD are taken seriously and are investigated immediately to determine the credibility and origin of the information , '' authorities said Wednesday . The two latest arrests were announced Friday . In one case , a man walked into the 28th precinct , approached a desk and harassed and threatened officers before being apprehended , police said . He faces charges of assault on a police officer , resisting arrest , obstructing government administration , criminal trespassing , disorderly conduct and harassment . In another case , a man noticed an off-duty officer on the street wearing part of his uniform under his jacket , police said . Authorities said the man verbally threatened the officer and made a firearm gesture with his hands . The off-duty officer called 911 , and the suspect fled . He was later found sleeping in the stairwell of a building nearby . The arrests come as an investigation continues into Ismaaiyl Brinsley , the 28-year-old who police say shot Officers Wenjian Liu and Rafael Ramos in Brooklyn . Hours before the officers were shot , Brinsley apparently posted on his Instagram account : `` I 'm putting wings on pigs today ... they take one of ours , let 's take two of theirs . '' Brinsley committed suicide after shooting the officers , police said . Among the other arrests this week , a 26-year-old allegedly posted pictures of weapons on his Facebook page along with threats to kill police officers , NYPD spokeswoman Sophia Mason said . The man 's Facebook post indicated that he wanted to kill two police officers , NYPD Detective Annette Markowski said . He was charged with making terroristic threats . Opinion : Dark times in a divided NYC . A 41-year-old also was arrested Wednesday on charges of aggravated harassment and making terroristic threats after he allegedly called into the 84th precinct -- where Liu and Ramos had been stationed -- and , requesting to speak to Ramos , asked whether the bullets had been removed from the dead officer 's head so `` he could kill more cops , '' Mason said . NYC mayor facing tensions further strained by police shootings . Police killer 's mother speaks . Of the arrests , police said , at least three stemmed from postings made on social media , and at least two came from misdemeanor charges of false report incident , in which the suspects allegedly called 911 reporting threats made by a third party that were later debunked . One arrest was made after the suspect phoned in a direct threat to 911 . And on Wednesday , a man was arrested on weapons , drug and harassment charges after he was overheard threatening to kill cops while talking on his cell phone inside a bank in Queens , according to the NYPD . That man is accused of saying on the phone that he was going to kill a cop , and that Brinsley should have killed white police officers , according to a criminal complaint filed in court . The complaint says that when police interviewed the suspect , he elaborated that two white officers should have been killed `` if the guy really wanted to send a message . '' In a tweet Thursday , Mayor Bill de Blasio thanked the police department and the civilian who saw something suspicious and acted : . `` Thank you to the NYPD officers who today arrested a man who threatened to kill cops , and to the good Samaritan who provided key information . ''
NYPD makes two additional arrests in connection with alleged threats . The first arrest was made at a home on the 200 block of East 149th Street around 1:30 a.m. Thursday. This follows the weekend killing of two officers in Brooklyn .