Judge orders suspect charged with shooting at Boston police officer held without bail

A 20-year-old man who allegedly fired a gun at an undercover Boston police officer as the officer sat in an unmarked vehicle on a Roxbury street Sunday was ordered held without bail Thursday following a dangerousness hearing in Roxbury Municipal Court.

“I’m going to find the defendant as dangerous,” said Judge Debra A. DelVecchio from the bench during the hearing for Alberto Polanco, 20, of Roxbury, who pleaded not guilty in the same courthouse Monday to charges of assault with a dangerous weapon, discharging a firearm within 500 feet of a building, and illegal possession of a firearm and ammunition.

According to a top Boston police commander and a Boston police report that is heavily redacted in some sections, the officer was sitting in the vehicle near 43 Waumbeck St. when the Shotspotter system recorded two shots being fired around 6:08 p.m. Sunday.

“Given the seriousness of the offense, [Polanco] poses a danger to the community and from what it looks like in the video to be the defendant firing two shots into the rear window of a car moving away from him, on someone he may or may not have known,” DelVecchio said during Thursday’s hearing.

Earlier in the hearing, a prosecutor said Polanco has an open gun case in Rhode Island.

“It’s the Commonwealth’s position that we have reason to believe Mr. Polanco is a member of H-Block” gang, Suffolk Assistant District Attorney Nathan McGregor said. “It’s fair to say that H-Block and the BPD Gang Unit have a significant presence in this courtroom right now, so make of that what you will.”

Polanco’s attorney, Thomas A. Silevitch, asked during the hearing that his client be released while the case was pending, saying he had no criminal record in Massachusetts and no problem with wearing a GPS on home confinement.

“There’s nothing to indicate he will not return to court, that indicate he will not abide by the laws of Massachusetts,” he said.

On the night of the incident, the officer quickly provided a description of the alleged shooter, later identified as Polanco, court papers show. During a series of conversations over the police radio that was recorded by Broadcastify.com, the officer shared some details of what had happened. After he described his alleged assailant, a 911 dispatcher had a question for him.

“Any direction of flight?’’ a 911 dispatcher asked him after she shared that description with other officers.

“No ma’am. I was in my vehicle. I had to get out of there,’’ the unidentified officer responded. “I’m not hit, I’m good. I’m on foot on Waumbeck, looking for this kid. ... He approached me on foot from Humboldt” Avenue.

According to the police report, responding officers reviewed security camera footage Sunday night that helped to identify Polanco as the alleged shooter. Police redacted the address of the camera that provided the “strongest and most convincing evidence” of the incident.

“Detectives reviewed the camera ... and identified Alberto Polanco walk across Humboldt Avenue to Waumbeck Street. Detectives observed Alberto Polanco wearing his distinctively identifying bright white T-shirt, black pants, and bright white sneakers ... and brandish a firearm and discharge two gunshots in the rear window,” of the unmarked vehicle the undercover officer was sitting in, police wrote in the report.

Officers then tracked Polanco to a Boston address and arrested him without incident about 45 minutes after the shooting, police wrote.

Polanco was arrested at his apartment in Roxbury, where police allegedly seized a Glock .22-caliber pistol and ammunition, the district attorney’s office said in a statement.

Polanco’s next court hearing will take place Oct. 27.

Material from prior Globe stories was used in this report.