The ex-con who allegedly sucker-punched a Bronx man into a coma was ordered held behind bars at a hearing Wednesday — where an NYPD detective and his own parole officer detailed how they tracked him down.

Both officers identified Bui Van Phu, 55, as the man seen in surveillance video slugging 52-year-old Jesus Cortes from behind, causing him to fall onto the sidewalk and hit his head, outside a Bronx restaurant on Aug. 12.

The NYPD released the footage last week in an attempt to find the attacker, and Phu’s parole officer, Denise Payano, testified Wednesday that she saw it on TV — and recognized Phu and told her boss at the agency.

Phu — a convicted sex offender who is on lifetime parole — then allegedly called her himself to confess to the crime, Payano told the court.

“I hit someone and he’s in the hospital. I don’t know if he’s dead,” he told the parole officer, according to the criminal complaint against him. “The police are looking for me.”

Phu, who was seated at a table wearing beige jail fatigues and a surgical mask, didn’t speak during hours-long parole hearing in Brooklyn Criminal Court.

He was arrested for attempted murder Aug. 17, but then cut loose without bail after being charged with assault and harassment, both misdemeanors, by the Bronx District Attorney’s Office.

Following outrage after his release, Gov. Kathy Hochul said she intervened and Phu was arrested on a state parole violation Friday.

Det. Julissa Flores, who spearheaded the investigation that led to Phu’s original arrest, testified Wednesday she first learned about the case when the victim’s brother reported him missing.

The two had been drinking with him at the Fuego Tipico Restaurant in The Bronx on Aug. 12, and Cortes’ brother grew alarmed when he didn’t come home the next day.

Flores was able to track Cortes down at a local hospital after reviewing 911 calls for injured persons and tracing one to the eatery on East 188 Street, she told the court.

At the same time, other cops from the 46 Precinct went to the restaurant and interviewed the owner, who told them first there had been a fight outside — but then changed his story and claimed someone had fallen and injured himself.

Flores went to a nearby smoke shop and retrieved video of the punch, which allegedly shows Phu coming up behind Cortes and knocking him out with a single blow.

The detective then sent out media and Crime Stoppers requests, as well as a facial recognition request that featured the video and a still image of the suspect.

When local media began playing the video, several tipsters who could identify the suspect contacted the NYPD, including Payano, Phu’s parole officer.

Payano said she was getting ready for work at about 6:45 a.m. on Aug. 17 when she saw the video and still image of the punch on News 12 Bronx and realized the suspect was her parolee.

She called her bureau chief and spoke with detectives, before getting the call from Phu, she testified.

Payano said she told Phu to stay at the homeless shelter where he was living and that detectives would come there and arrest him.

Phu’s court-appointed attorney, Jonathan Stonbely, argued the state had not sufficiently proven his client was the suspect on the video, and that they had not identified a specific crime committed for him to have violated his parole.

The preliminary hearing officer, Patrice Brathwaite, ordered Phu jailed at least until his final parole revocation hearing on Sept. 12.

The victim’s brother, Juan Cortes, told The Post on Sunday that his brother — who suffered bleeding to the brain and was placed in a medically induced coma after the attack — was on the mend.