Authorities on Friday began to paint an image of the Bronx man charged with driving through Times Square crowds as an intentional killer who paused to let traffic go by before suddenly accelerating onto the sidewalk and mowing down 21 pedestrians, including a teenage tourist who died in the rampage.

“He waited for those cars to pass and he accelerated, striking down those pedestrians,” William Aubry, NYPD Chief of Manhattan South Detectives, said Friday. “That goes to the state of mind.”

Richard Rojas, 26, did not enter a plea to one count of second-degree murder, 20 counts of second-degree attempted murder and one count of aggravated vehicular homicide during a short appearance at Manhattan criminal court Friday.

A handcuffed Rojas said nothing as Judge Tamiko Amaker ordered him held without bail, and his defense attorney, Enrico DeMarco, declined to comment after the hearing. Rojas’ family members attended the hearing but also did not comment.

Manhattan Assistant District Attorney Harrison Schweiloch, who asked for Rojas to be remanded, said in court that Rojas went on a “murderous rampage against our city.”

He drove from the Bronx to Times Square “without incident,” the prosecutor said, but he drove to Seventh Avenue and “waited for traffic to move, made a U-turn, hopped the sidewalk . . . he murdered in cold blood an 18-year-old woman.”

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Rojas “only stopped . . . after his car crashed into a metal post,” the prosecutor said.

A criminal complaint said Rojas “ran at” a police officer after crashing his vehicle into the pedestrians and told the officer: “I wanted to kill them.”

Before the crash on Thursday, Rojas left his Bronx home at 10:30 a.m., heading to Manhattan, according to a timeline of events laid out by Aubry at a Friday news conference in Times Square.

A half-hour later, Aubry said Rojas was recorded entering Manhattan, and at 11:50 a.m. he was at West 48th Street and Seventh Avenue.

Rojas waited on Seventh Avenue at 42nd Street for traffic to pass, then made a right turn onto the sidewalk, striking 18-year-old Michigan tourist Alyssa Elsman between 42nd and 43rd streets, and continuing on to hit others, Aubry said.

Parts of his car flew off as he struck people and objects, and at one point he drove under scaffolding on the sidewalk, he said.

After his vehicle was stopped by a metal bollard, Rojas got out, only to be tackled by a traffic agent, on- and off-duty police officers, and a security guard, Aubry said.

Court documents said Rojas had “glassy eyes, slurred speech and was unsteady” when detectives interviewed him soon after the noontime crash. Rojas had admitted to smoking marijuana laced with PCP, according to the complaint.

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Investigators now are waiting for the results of blood tests to confirm what substances Rojas was on, Aubry said.

“I can’t comment on the exact chemical substance,” he said. “We hope blood work comes back in the next few days to confirm what we believe.”

Of the 20 victims who survived, 19 were taken to hospitals, and seven were admitted, Aubry said. On Friday, three victims remained in critical condition and one, a 38-year-old woman from Canada, was in “very critical condition,” he said.

Elsman’s 13-year-old sister, who was among those injured, was being treated at NewYork-Presbyterian Hospital/Weill Cornell Medical Center for a collapsed lung and a broken pelvis, Aubry said.

Detectives on Friday searched Rojas’ Bronx home for evidence, at one point removing what appeared to be a rug wrapped in opaque plastic.

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Aubry said police had sought a search warrant for the house and added that Rojas’ mother, with whom he lived, was being cooperative. Neighbors said they didn’t know Rojas.

Investigators also were continuing to search Rojas’ vehicle — which was registered to him — but that search so far has yielded nothing “out of the ordinary,” Aubry said.

He said investigators were poring through Rojas’ background, including any history of “psychological illness.” Rojas had served in the Navy from 2011 to 2014, Aubry said.

Rojas had been arrested in the Bronx for harassment in the past month, but pleaded it down to harassment, Schweiloch said. Rojas also has two DWI convictions, from 2015 and 2008.

Meanwhile, in response to the tragedy, police on Friday added extra security measures to the Times Square area, including heavy Jersey barriers and other covert systems.

Aubry noted if not for the security devices that already existed — specifically a metal bollard that had stopped Rojas’ car at 45th Street — more lives could have been lost.

“There are many more people who would have been killed if it had not been for the security measures on 45th Street,” he said.

With Mark Morales