The suspected gunman in the cold-blooded killing inside a Harlem smoke shop was arrested early Tuesday – and tied to another deadly shooting that happened a day earlier in broad daylight, cops said. 

Messiah Nantwi, 21 – last arrested two years ago for shooting at Bronx cops, who returned fire and gravely wounded him – was tracked down through a CrimeStoppers tip and nabbed in connection to the deadly Sunday encounter inside the smoke shop on Malcolm X Boulevard near West 125th Street, authorities said. 

The 36-year-old victim — whose name had not been released by Tuesday morning — was shot in the head following an exchange of words with Nantwi minutes before 8 p.m., according to the NYPD and chilling video obtained by The Post. 

In the footage, the shooter and the victim are seen arguing for several seconds in front of a group of men.

The victim then turns to leave, but as he is heading for the exit, the suspect pulls a gun out of his pocket and blasts the victim in the head.

The victim collapses to the floor but is still moving and appears to try to get up, before the calm attacker shoots him in the back in cold blood, as seen in the recording.

The final seconds of the video show the shooter walking out of the store.

The victim was taken to Harlem Hospital, where he was pronounced dead.

Nantwi was charged with murder and criminal possession of a weapon in connection to that shooting, authorities said. 

He was also linked to a second shooting about a half-mile away, which happened around 4:40 p.m. Saturday at Madison Avenue and East 132nd Street, cops said. 

Jaylen Duncan, 19, was shot in the head and rushed to Harlem Hospital, where he was pronounced dead, authorities said. 

Nantwi — a Harlem resident himself — was charged with murder in that case, police said.

The motive for that slaying remained unclear Tuesday. 

Investigators do not believe Nantwi knew Duncan, or the victim in the smoke shop murder, cops said. 

Nantwi was last arrested back in February 2021 for allegedly firing at NYPD officers who tried to arrest him – and an accomplice – for allegedly spray-painting graffiti in the Bronx, authorities said. 

“As the officer struggled with the man in an attempt to arrest him, the suspect pulled out a semi-automatic handgun and fired at least three times at the officers,” then-NYPD Chief of Department Terence Monahan said at the time.

“It was at this time that all three officers engaged the man, returning fire — striking him numerous times,” Monahan said.

The officers were not hurt, but Nantwi was taken to Lincoln Medical Center with what were initially described as critical injuries. 

Nantwi recovered and was charged with three counts of attempted murder on a police officer, cops said. 

Records show that was initially ordered held without bail in connection to that case, but a judge later held him on $500,000 bail. 

He entered a “not guilty plea,” the records show. 

The circumstances of his release were not immediately clear.