Heriberto Suazo (left) and Amaury Rodriguez, two of the three men gunned down near Columbia University. (
)

Police are looking for assistance in locating the suspect above. (
)

The three men found gunned down inside a BMW near Columbia University yesterday had been robbing drug dealers and may have been killed in retaliation, police said.

Victims Luis Catalan, 25, Heriberto Suazo, 26, and Amaury Rodriguez, 30 — all Manhattan residents — were marijuana traffickers with extensive criminal records, police spokesman Paul Browne told reporters today. The three men were shot dead execution-style at around 5:30 p.m. by a lone gunman one police source described as a “cool customer.”

“They’ve all been robbed by drug dealers, or on the other end they’ve robbed drug dealers,” said a police source. “They flip back and forth robbing each other. This time, it was the end for them.”

Cops this afternoon released surveillance video that shows a man they suspect was involved in the cold-blooded killing.

Police said the gunman was seated behind the driver in Suazo’s luxury sedan when he opened fire.

Catalan, who was on the right side of the back seat, died first, said cops. The gunman shot him in the left temple and left side before turning the gun on Rodriguez, who was the driver, and Suazo, who was in the front passenger seat. None of the victims were armed.

“It would appear that a lone gunman quickly shot and killed these three young men, and then calmly walked away from the crime scene,” Browne said.

The shooter left behind no shell casings, leading police to assume he used a revolver. It was possible the gun had a silencer, but that was a moot point, said Browne, since the shooting happened on a quiet section of West 122nd Street near Grant’s Tomb.

No one in the Columbia University or Manhattan School of Music classrooms nearby heard anything, cops said.

The bodies sat in the car for about an hour before a passerby noticed the men seated dead in the car, slumped against the car’s tinted windows in their blood-drenched clothes.

Suazo was busted in Yonkers last September with 12 pounds of hydroponically-grown marijuana and two pistols, a .380-caliber semi-automatic and a .25 caliber semi-automatic.

He and Rodiguez were wanted in connection with recent a non-fatal shooting in Washington Heights. Neither was the shooter, but the men allegedly beat the victim in the incident.