For the third time in just four days, a cop shot a thug menacing him with a weapon — this time after the man, who was involved in stripping car parts, refused to drop his knife, police said.

Sgt. Joe Alohan shot the man in the torso, but he still ran off, leaving a trail of blood stretching two blocks from East 19th Street near Glenwood Road in Brooklyn at about 4 a.m. Friday.

The shooting came two days after another sergeant and cop shot a man dead in The Bronx after he pistol-whipped his girlfriend and then turned his gun toward the officers.

Twelve hours before that, a detective shot a man in East Harlem who was shooting it out with another thug Tuesday night.

Going into the week, there had been a total of eight police-involved shootings for the year. Police union leaders blame the surge on criminals who have become increasingly aggressive because they no longer fear cops.

“These streets are become more dangerous and attacks on law enforcement more frequent,” said Ed Mullins, president of the Sergeants Benevolent Association.

PBA President Pat Lynch was in agreement.

“The solution is to bring the NYPD back to Safe Streets Safe City program levels and for the city to stand behind and support police officers,” he said.